New Series of Consumer Price Index Numbers for Industrial Workers
on base 2001=100
Labour Bureau, since its inception, has, inter-alia, been entrusted with the responsibility
of compilation and maintenance of the Consumer Price Index Numbers for Industrial Workers
(CPI-IW). The CPI-IW purports to measure the temporal change in the retail prices of fixed
basket of goods and services being consumed by the target group i.e. an average working class
family and thus, is an important indicator of the retail price situation in the country. The CPI-IW
is mainly used for the determination of dearness allowance being paid to millions of
Central/State Government employees as also to the workers in the industrial sectors besides
fixation and revision of minimum wages in scheduled employments. The main objective of the
CPI-IW (new series) was to update the base year of the previous series of Consumer Price Index
Numbers for industrial workers (Base 1982=100) to 2001=100.
2. MAIN CONSTITUENTS
Three most important constituents of the CPI-IW are the centre specific weighting
diagrams, the retail price data and the house rent data.
A. Updation of Weighting diagrams
(I) Conduct of Income & Expenditure Survey:
The field staff of the National Sample Survey Organisation (NSSO) through a detailed
questionnaire collected the income and expenditure data in order to reflect the change in the
consumption pattern of the working class population at all the 78 selected centres across the
country during 1999-2000 under the overall guidance and supervision of the Labour Bureau.
Detailed instructions were issued by the Labour Bureau for canvassing of schedules by the field
staff in order to ensure uniformity in collection of data having emphasis on its accuracy. Besides,
extensive training was imparted to the Officers/Officials of the NSSO at different places by the
Labour Bureau before the launch of the actual work.
(II) Scrutiny of Schedules:
Two levels of scrutiny ensured the reliability and authenticity of data collected from the
field. At the first level, the NSSO made elaborate arrangements for field scrutiny of canvassed
schedules on the basis of field scrutiny manual circulated by the Labour Bureau. Thereafter,
these schedules were again scrutinised in detail by the Labour Bureau to ensure consistency in
the collected data. Discrepancies revealed during the course of the scrutiny were reconciled by
referring the scrutiny points to the respective RO/SRO of the NSSO and also by making actual
visits to the field.
(III) Tabulation of data:
The responsibility for computerised processing and tabulation of data under the new
series was entrusted to the Regional Computer Centre (RCC), now known as DOEACC,
Chandigarh, which had undertaken this assignment earlier also under the previous series. The
tabulation was done on the basis of the estimation procedure and tabulation plan duly approved
by the Technical Advisory Committee on Statistics of Prices and Cost of Living (TAC on
SPCL). In this regard detailed instructions were supplied to the RCC. The entire exercise which,
inter-alia, included data entry, data cleaning, generation of tables at sub-sample/sector/centre
levels and their validation, were completed with the active support of the Labour Bureau.
(IV) Derivation of Weighting Diagrams:
The weighting diagrams for the purpose of compilation of index numbers had been
derived on the basis of average monthly family expenditure. The average budget derived from a
family budget enquiry consisted of all items of expenditure reported by the families surveyed.
These items of expenditure can be broadly divided as;
Non-Consumption Expenditure; and
Only consumption expenditure has been considered for the purpose of a weighting
diagram for construction of consumer price index series as is the usual practice followed
everywhere. Non-Consumption expenditure and expenditure on Capital outlays like income tax
and other direct taxes, charities and gifts, interest on debts, repayment of debts, litigation
expenses, life insurance premium etc. have not been included in the index basket.
The consumption groups commonly adopted for working class consumer price index
numbers are as follows:
IA - Food
IB - Pan, Supari, Tobacco & Intoxicants
II - Fuel and Light
III - Housing
IV - Clothing, Bedding and Footwear
V - Miscellaneous.
The Food Group and the Miscellaneous Group have been further divided into sub-groups
Cereals & Cereal Products
Pulses and Pulse Products
Oils and Fats
Meat, Fish and Eggs
Milk and Milk Products
Condiments & Spices
Vegetables & Fruits
Education, Recreation & Amusement
Transport & Communication
Personal Care & Effects
B. Updation of retail price data
(I) Organisation of Price Collection Work:
Before the launch of the main survey, pilot surveys on scientific lines were conducted at
all the 78 centres to demarcate the centre-boundaries with a reference to market selection;
selection of markets & shops; testing and finalisation of price collection schedule alongwith
fixation of specifications of the items to be priced; setting up of price collection machinery in
consultation with State Govt. by appointing Price Collectors/Supervisors and fixation of price
collection day. With the setting up of price collection machinery, retail prices from 289 selected
markets started flowing into the Labour Bureau. Initially, a very exhaustive price collection
schedule was introduced in the field, which was pruned in the beginning of the year 2000 on the
basis of actual expenditure reported in the first four sub-rounds of the main survey except for
seasonal items. These schedules were again revised on the basis of actual weighting diagrams
and would continue throughout the lifetime of the series.
(II) Study of the Run of Prices:
The retail prices are collected on a weekly/monthly basis by the Price Collectors through
personal visits to the selected/reserved shops in the markets on the appointed price collection day
every week/month. The work of the Price Collectors is also being supervised by the Price
Supervisors. Both the Price Collectors as well as the Price Supervisors are employees of the
respective State Governments who work on part-time basis in lieu of which some honorarium is
paid to them by the Labour Bureau. There is a State Co-ordinator who is the overall incharge for
the Price Collection work for the entire State. Besides, the officials of the different Regional
Offices/Sub-Regional Office of the Labour Bureau undertake periodic price audit work at
different centres on a regular basis. Prices for each commodity are collected from two selected
shops of each of the selected markets. The prices collected from the field are subjected to
detailed examination from the point of view of consistency on account of inter-shop, intermarket and inter-period variations. Discrepancies wherever found are referred to the field and
prices are rectified accordingly before utilising the data for index compilation. The seasonal
pattern as reflected in the price movement has been specially looked into. The weekly/monthly
quotations are first averaged at market level for a month and by pooling the market averages the
Centre level average price for an item for a month is arrived at.
C. Conduct of Repeat House Rent Surveys
The change in rent and related charges, which constitute a single item under housing
group, is captured through Repeat House Rent Surveys, which are conducted in the form of sixmonthly rounds. The survey is conducted on a sub-sample of dwellings covered during the main
income & expenditure survey in 1999-2000. The index for the housing group is revised twice in
a year i.e. in January and July of every year. The index is calculated once in every six months
and is kept constant for the entire six months on account of the tendency of house rent to remain
more or less stable over short periods. Under the house rent survey, three types of dwellings viz.
Rented, Rent free and Self-owned (Owner occupied) are covered uniformly across all the
centres. This practice was also followed in the previous series of the CPI-IW (1982=100).
3. FINALISATION OF BASE YEAR:
The well-known criteria used for the selection of base year are:
The base year should preferably synchronise with the period of the income & expenditure
survey and should not be very distant from the actual period of the survey.
Reliable price data should be available for the chosen period.
The base year should be a normal year i.e. a year in which there is no abnormalities in the
price level and price variations.
The base year of the constituent centres should be uniform so as to facilitate easy and quick
compilation of the All-India Index.
Though the price data were being collected and dispatched to the Labour Bureau
immediately after setting up of the Price Collection machinery from majority of the centres, yet,
prices could be stabilised in strict sense from all the 78 centres only in the year 2001.
Accordingly, calendar year 2001 has been taken as the base for all the centres under the new
series. Apart from the reliability of price data, selection of calendar year 2001 as the base year
also seemed to be justified keeping other factors into consideration. Going by the broad
economic indicators the overall price behaviour across the country was more or less normal.
4. METHODOLOGY FOR COMPILATION OF INDICES:
The most preferred index formula used for compilation is the Laspeyre‟s base weighted
formula because of its inherent practical advantages. The formula in its aggregative form is
expressed as below;
S Pn Qo
-------- x 100
S Po Qo
The operational form of the formula is obtained by adjusting the numerator S Pn Qo as S Qo Po
x (Pn / Po) which is simply an alternative algebric expression without changing its significance
or value and is given as;
SQo Po x (Pn / Po ) x 100
----------------------------S Qo Po
where Qo Po denotes the expenditure on an item in the base period and is termed as the
weight and ( Pn / Po ) X 100 is called Price Relative, which is the ratio of the current period price
to base period price of an item.
5. CONSTRUCTION OF INDICES
i) Centre Specific indices
Centre specific indices in respect of all the 78 centres are being compiled on month to
month basis by utilizing the expenditure on an item in the base period and the ratio of current
period price to base period price of an item.
ii) Index for Housing Group
As a natural corollary to the index, house rent data, is being collected for compilation of
house rent indices through the Repeat House Rent Surveys on a six month round basis. So far,
the fieldwork upto 8th rounds has been completed and the fieldwork for the 9th round is,
currently, in progress.
iii) Construction of All India Index
The All India Index is the weighted average of the 78 centre level indices. The centre
weights are being determined as the ratio of product of average consumption expenditure per
family as per the main survey and the number of Working Class Families represented by a centre
in a State to sum of such products over all the centres. In order to pre-empt over weighting to
big cities in respect of their contribution to All India Index, each centre is assumed to represent
an equal share of the number of working class families within the State. In case the actual
working class population (as per the main survey) for a particular centre exceeds the
proportionate share accruing to the centre, the actual population of the centre is taken to
determine its share and the remainder of the working class population in the State as a whole is
equally distributed amongst remaining centres in the State.
EXAMINATION AND APPROVAL OF TECHNICAL DETAILS
The Technical Advisory Committee on Statistics of Prices and Cost of Living (TAC on
SPCL) got examined all the technical details pertaining to updation of the CPI-IW (1982=100) to
a recent base by a Sub-group of the TAC. The Sub-group comprised of Director General & Chief
Executive Officer, NSSO, M/o Statistics & Programme Implementation as the Chairman and
Director General, Labour Bureau; Deputy Director General, Central Statistical Organisation;
Adviser M/o Finance; Economic Adviser M/o Industry; Adviser, DESACS RBI, Mumbai &
Prof. Abhijit Sen, JNU as Members. The recommendations of the Sub-Group were placed before
the TAC on SPCL for its consideration and approval in the 43rd meeting held on 15.07.2004
wherein the TAC accorded its approval to the methodology for compilation of indices under the
CPI-IW (new series).
CONSULTATION WITH USERS’
In line with the recommendations of various Committees regarding involvement of
Users i.e. representatives of the Employers, the Employees (Trade Unions) and the State
authorities at different stages of the exercise for updation of the base to ensure wider
participation and enhanced acceptance, Labour Bureau had a series of consultations with these
bodies at various Centre and State levels during the setting up of the Price Collection Machinery
at the 78 selected centres under the CPI-IW (New Series). The active involvement of these
agencies besides the Planning/Labour Departments of the State Governments go a long way in
ensuring desired level of transparency in the compilation of these indices, which in turn provides
credibility and wider acceptance. Since the CPI-IW is primarily used for determining the amount
of dearness allowance to be paid to millions of industrial workers in Public/Private sectors and
employees of Central/State Governments, it has therefore, been a continuous endeavour on the
part of the Labour Bureau to involve users at various stages of updation processes of the index
8. MEETING WITH USERS’ PRIOR TO THE RELEASE OF THE INDEX
A two day National Level Index Users‟ Meeting was organized on 19th-20th May,
2005 at Shimla in connection with the release of the new series of the CPI-IW. The
representatives of Central/State Ministries/Departments, Employers‟ Associations and Central
Trade Unions participated in the deliberations in the Tripartite Meeting. The meeting was
convened to seek the tripartite concurrence for the release of the CPI-IW (New Series) on base
2001=100, which was to replace the existing series of the CPI-IW (1982=100). All the technical
issues relating to compilation of the CPI-IW 2001=100 series as well as the process for regular
consultation with the Users‟ especially the Central Trade Unions and Employers‟ Organizations
were discussed. There was a broad consensus so far as the technical aspects of the exercise was
concerned. Nonetheless it was decided to “address the issues pertaining to participation of the
Central Trade Unions as well as the Employers‟ Organizations in the deliberations of the
Technical Advisory Committee on Statistics on Prices & Cost of Living (TAC on SPCL) besides
evolving a suitable mechanism for periodic involvement of the users‟ during the conduct of the
entire exercise, prospectively, for future revision of base”, in a meeting to be chaired by the
Hon‟ble Labour & Employment Minister with the representatives of Central Trade Unions.
As a follow-up of the National Level Index Users‟ Meeting, a meeting with the
representatives of Central Trade Unions was held on 9th September 2005 in the Ministry under
the Chairmanship of the Secretary, Labour & Employment. The issues discussed pertained to the
participation of the Central Trade Unions and the Employers‟ Organizations in the TAC on
SPCL. It was decided that a meeting of the reconstituted TAC on SPCL having the members
from the Central Trade Unions and Employers‟ Organizations would be held prior to the release
of the new series of CPI-IW on base 2001=100.
The 45th meeting of the TAC on SPCL was, therefore, held on 17th February, 2006,
wherein 3 representatives each of the Central Trade Unions and the Employers‟ Organisations
participated in its deliberations on the release of the new series of CPI-IW on base 2001=100.
After discussions the TAC on SPCL decided that in view of improvements made in the new
series as also the urgent need for updated base, the CPI –IW ( New Series) should be released.
Accordingly, with the approval of Govt. of India, the Labour Bureau released the new series of
the CPI-IW on base 2001=100 with effect from January, 2006 index on 9th of March, 2006. The
details of Centre-wise and All-India Index Numbers alongwith Linking Factors with previous
series of CPI-IW on base 1982=100 may be seen in the Table Nos. A.1.1.1 and A1.1.2 of this
issue of the Indian Labour Journal.
About the Price Index
The price index is an indicator of the average price movement over time of a fixed basket of
goods and services. The constitution of the basket of goods and services is done keeping in to
consideration whether the changes are to be measured in retail, wholesale, or producer prices etc.
The basket will also vary for economy-wide, regional, or sector specific series. At present,
separate series of index numbers are compiled to capture the price movements at retail and
wholesale level in India. There are four main series of price indices compiled at the national
level. Out of these four, Consumer Price Index for Industrial Workers (CPI-IW), Consumer
Price Index for Agricultural Labourers / Rural Labourers (CPI -AL/RL), Consumer Price Index
for Urban Non-Manual Employees (CPI-UNME) are consumer price indices. The Wholesale
Price Index (WPI) number is a weekly measure of wholesale price movement for the economy.
Some states also compile variants of CPI and WPI indices at the state level.
WPI is also compiled by many states covering state level wholesale transactions. Presently WPI
series compiled are -- Assam (base 1993-94), Bihar (1991-92), Haryana (1980-81), Karnataka
(1981-82), Punjab (1979-82), U.P.(1970-71) and West Bengal (1980-81). Most of the state series
are cover agricultural commodities only.
Step-wise introduction to compilation of WPI
Like most of the price indices, WPI is based on Laspeyres formula for reason of practical
convenience. Therefore, once the concept of wholesale price is defined and the base year is
finalized, the exercise of index compilation involve finalization of item basket, allocation of
weights (W) at item, groups/ sub-groups level. Simultaneously, the exercise to collect base prices
(Po), current prices (P1), finalization of item specifications, price data sources, and data
collection machinery is undertaken. These steps are discussed in detail in the following sections :
1) Concept of Wholesale Prices:
Wholesale price has divergent connotations adopted by the different departments using them.
There is no uniform definition for agricultural and non- agricultural commodities as all the
wholesale prices can not be collected from the established markets.
Agricultural commodities: In practice, there are three types of wholesale markets viz., primary,
secondary and terminal in the agricultural sector. The price movements and price levels in all
three vary. Price movement in the terminal market may tend to converge toward the retail prices.
Option to collect the wholesale prices for these three different stages of wholesale transactions
exists for agricultural commodities though the primary market is prepared.
Ministry of Agriculture has defined wholesale price as the rate at which relatively large
transaction of purchase, usually for further sale, is effected. Various state agencies concerned
with the collection of wholesale prices of agricultural commodities are following the concept of
Ministry of Agriculture. However, there are certain variation with regard to inclusion or
exclusion of incidental charges, duties and taxes. For e.g., in Andhra Pradesh, the wholesale
prices include incidental charges such as weighment charges, cost of bags and sales tax. In
Gujarat, the wholesale prices are inclusive of packing charges and taxes. In Punjab and Tamil
Nadu, the wholesale prices are inclusive of incidentals. In Haryana, the wholesale prices for
agriculture commodities exclude taxes but include arat, weighment and the lorry charges,
whereas, non-agricultural products include sales tax, etc.
Non-agricultural commodities: For non-agricultural commodities, which are predominantly
manufacturing items, the problem arises, as there are no established sources in markets. This is
true of mining and fuel items also. The issue of ex-factory vis-à-vis wholesale prices for nonagriculture items have been discussed by the successive Working Groups set up for the revision
of WPI and all have reached the conclusion that in practice, it is not feasible to collect wholesale
prices for most of the manufacturing items. It has also been observed that the margin of
wholesalers in case of non-agricultural commodities remains unchanged for over a long period of
time. As a result, it is felt that the trends in the index compiled on the basis of ex-factory prices
would not be much different from the index if compiled on the basis of wholesale prices if it
were feasible to get these prices.
The last Working Group has recommended collecting
wholesale prices from the markets as far as possible, because the economy is moving towards
globalisation and open trade with inputs increasing in the commodities set.
The wholesale price as defined for WPI: The concept of wholesale price adopted in practice
represent the quoted price of bulk transaction generally at primary stage. The price pertaining to
bulk transaction of agricultural commodities may be farm harvest prices, or prices at the village
mandi /market of the Agricultural Marketing Produce Committee/ procurement prices, support
prices. For manufactured goods the wholesale prices are administered prices, ex- factory gate/
ex-mill, ex-mine level. Ex- factory prices exclude rebate if any, other taxes and levies are
excluded though excise duty is currently included.
Wholesale price and producer price: The wholesale price as defined above differs from
producer (output) prices as the latter excludes all kind of taxes and transport charges. In 1993
SNA, Producer(output) price is defined as the amount receivable by the producer from the
purchaser for a unit of a good or service produced as output minus VAT or similar deductible
tax, invoiced to the purchaser. It excludes any transport charges invoiced separately. It excludes
any transport charges invoiced separately by the producer. However, the producer (input) prices
include retail or wholesale margins.
2) Choice of Base Year :
The well known criteria for the selection of base year are (i) a normal year i.e. a year in which
there are no abnormalities in the level of production, trade and in the price level and price
variations, (ii) a year for which reliable production, price and other required data are available
and (iii) a year as recent possible and comparable with other data series at national and state
level. The National Statistical Commission has recommended that base year should be revised
every five year and not later than ten years.
3) Selection of Items, Varieties/ Grades, Markets:
To ensure that the items in the index basket are as best representatives as possible, efforts are
made to include all the important items transacted in the economy during the base year. The
importance of an item in the free market will depend on its traded value during the base year. At
wholesale level, bulk transactions of goods and services need to be captured. As the services are
not covered so far, the WPI basket mainly consists of items from goods sector. In the absence of
single source of data on traded value, the selection procedures followed for agricultural
commodities and non-agricultural commodities have also been different.
Agricultural commodities: As there is a little scope of emergence of new commodities in the
agriculture, the selection of new items in the basket is done on the basis of increased importance
in wholesale markets. Varieties, which have declined in importance, need to be dropped in the
revised series. Final inclusion or exclusion of an item in the basket is based on the process of
consultation with the various departments. The exercise of adding /deleting commodities,
specifications and markets is completed once the consultation process is over. In the existing
WPI series, items, their specifications and markets have been finalized in consultation of with the
Directorate of E&S (M/O Agriculture), National Horticulture Board, Spices Board, Tea board,
Coffee Board and Rubber Board, Silk Board, Directorate Of Tobacco, Cotton Corporation of
Mining Items: For deciding on the inclusion and exclusion of mineral items, their grades,
market centers etc. suggestions of Indian Bureau of Mines are taken into account. Specifications
of coal, coke and lignite have been decided in consultation with the Department of Coal.
Likewise for selection of petroleum products the Ministry of Petroleum is consulted and for
electricity suggestions are taken from Central Electricity Authority.
Manufactured Products: Selection of items from manufacturing sector, as a whole, is the most
tedious and time taking process. To ensure complete coverage, selected items have to represent
not only the organized manufacturing sector but also vast informal sector.
Organized Manufacturing Sector: Regular time series data on value of production are
available through Annual Survey of Industries covering factory sector. The criterion for selection
of items has been based on the cut off traded value of a product during the base year. The traded
value of a product is the sum total value of output as per ASI base year+ Excise duty + Imports
during base year- Exports during the base year. WPI 1993-94 adopted a cut off traded value of
Rs. 120cr. All possible efforts are made to establish a proper concordance between the NIC
classification adopted in ASI and ITC (HS) classification for imports and exports quantum. The
problem of concordance arises in case of textile items and for this segment; the selection of items
has been done with the help of Office of the Textile commissioner. Some of the items may not
feature in the final basket even though the traded value is above the cut off point. This may be
due to poor specifications or non-availability of regular data source for continuous pricing.
Unregistered / unorganized manufacturing sector: Units falling in this sector add
substantial portion to the total manufacturing production in the economy. Unorganized
manufacturing sector covers traditional sectors like handlooms, sericulture, coir, khadi and
village industries and modern segments like SSI and power looms. Further the small-scale sector
encompasses both organized and unorganized segments of the manufacturing sector. But for
informal sector, all encompassing time series data on value of production are not available. In the
past, Working groups have made efforts to pool value of production data from disparate sources
like results of surveys on Own Account Enterprise (OAE), Directory Manufacturing
Establishment (DME) and Non-Directory Manufacturing Establishment (NDME), Economic
Census and its follow up surveys and Census of Registered SSI units. The last Working group
could not use these data sources mainly because it found the data available either farther from the
chosen base year or were incompatible. However, some items from silk. coir, power looms and
handlooms based were included on the suggestions of agencies responsible for these segments.
The selection of specification/ grade/ variety in respect of manufactured products as also the
selection of sources for supplying regular price data is done with help of production data.
Selection of data sources is done on subjective sampling basis. For each item, a list of 10 major
manufacturers/ producers is prepared and efforts are made to seek willing cooperation from the
top five manufacturers for regular supply of weekly wholesale price quotations. Data collection
is done on conditions of confidentiality. At least five price quotations in respect of representative
grades are included in the index. In case there are less then five manufacturers of an item, then
all the units are roped in to furnish the price data.
4) Derivation of Weighting Diagram :
Weights used in the WPI are value weights not quantity weights as its difficult to assign quantity
weights. Distribution of the appropriate weight to each of the item is most important exercise for
reliable index. Unlike consumer price indices, where weights are derived on the basis of results
of Expenditure Surveys, several sources of data are used for derivation of weights for WPI.
Because of non-availability of updated Supply and Use Table (SUT), the approach, finding
favour with the successive Working groups, is based on top down stratified compartmentalized
system. Under this approach, weights are first assigned at Major group level from outside with
due account made for exclusion of services from the total value of transactions in the economy.
This method for weighting diagram represents more accurately structural changes at higher level
of aggregation. Further, compartment system also ensures that wherever data for a more recent
year are available they can be used, while in other compartments data from more distant year can
be achieved. This has also made it possible to use different sets of data sources for agricultural
and manufacturing items.
Weights of Agriculture commodities: For building of the weights of agricultural commodities,
the data on sale of agricultural commodities is not available as there is large number of markets.
Therefore, to arrive at the approximate traded value of agricultural commodities; an indirect
method of arriving such estimates is used. These weights are based on the Marketed value
(MV) arrived at by multiplying Marketed Surplus Ratio (MSR) to the estimates of Value Of
Production (VOP) of agricultural commodities. The estimates of VOP are based on the estimates
of quantity of production, as brought out by the Directorate of Economics and Statistics(DES),
and an average price of a commodity.
The ratio of quantity marketed to quantity produced gives the MSR.
R = ---------- = ------------------------QOP
Quantity of Production
The estimates of MSRs are based on the results of Comprehensive Scheme on Cost of
Cultivation of DES and other sources. The Directorate of Marketing and Inspection, M/O
Agricultural, is also responsible to generate MSRs.
In practice MSRs are worked out on the basis of production value of three years average
production to remove the bias on account of fluctuation in individual commodity and over all
production. No estimates of MSRs are available in the case of new items of fruits, vegetables and
flowers, and these are finalized separately by the working group, based on the related crops.
MSRs of flowers and meat items are kept 100 considering that production of these is mainly for
Manufactured items: As discussed above, the traded value of manufactured products i.e., total
production + excise duty+ imports - exports value for the year are worked out from various
sources. Final weights of each item is based on its traded value plus pro rata imputed traded
value of items which need to be excluded from the basket due to various reasons.
In the current series traded value of items falling under „Other manufacturing‟ have been
imputed amongst other items in the remaining sub-groups of „Manufactured products‟ as there
was only one item featuring above the cut-off mark. Retaining it would have led to extreme
fluctuations. Similarly weight of crude petroleum was distributed pro rata amongst fuel items, as
procuring its wholesale prices was not possible.
5) Collection of Prices:
In WPI pricing methodology used is specification pricing. Under this, in consultation with the
identified source agencies, precise specifications of all items in the basket are defined for repeat
pricing every week. All characteristics like make, model, features along with the unit of sale,
type of packaging, if applicable, etc are recorded and printed in the price collection schedule. At
the time of scrutiny of price data all these are kept in mind. This pricing to constant quality
technique is the cornerstone of Laspeyres formula. In case of changes in quality and
specifications, due adjustments are made as per the standard procedures.
The collection of base prices is done concurrently while the work on finalisation of index basket
is on. Therefore, price collection is normally done for larger number of items pending
finalisation. Once the basket is ready, current prices are collected only as per the final basket
from the designated sources. Weekly prices need to be collected for pre-determined day of the
week. For the current series prices are quoted on the basis of the prevailing prices of every
Friday. Agricultural wholesale prices are for bulk transactions and include transport cost. Nonagricultural prices are ex-mine or ex-factory inclusive of excise duty but exclusive of rebate if
6) Treatment of prices collected from open market & administered prices:
There are some items which constitute part of index baskets but the prices for these items are
either totally administered by the Government or are under dual pricing policy. The issue of
using administered prices for index compilation is resolved by taking into account appropriate
ratio between the levy and non-levy portions. Where these ratios are not available, the issues can
be resolved through taking the appropriate number of price quotations of the administered prices
and the open market prices after periodic review.
Due to variation in quality and different price movements of the commodities belonging to
unorganized sector, separate quotations from organized and unorganized units have to be taken
and merged based on the turnover value of both the sectors at item level. For pricing from
unorganized sector, adequate number of price quotations has to be drawn out of the list of units
by criteria of share of production as far as possible.
7) Classification structure:
The Working Groups over the period have been suggesting to bring the classification of various
items under different groups and sub-groups as per the latest revised National Industrial
Classification (NIC) which in turn is comparable to International Standard Industrial
Classification (ISIC). The classification based on NIC renders the WPI data amenable to
comparison with the Index of Industrial Production (IIP) and National Income data.
The grouping and classification of WPI is also useful for in depth analysis as separate inflation
rates can be worked out for groups with items whose prices are given to extreme fluctuations,
affected by international prices or have administered prices. Apart from the headline inflation
based on WPI, core inflation, manufactured products inflation, primary articles inflation etc. can
be easily computed. The classification structures adopted in the WPI (1993-94) series is as
II. Fuel, Power, Light
I. Primary Articles
III. Manufactured Products
Rubber & Plastic products
Chemicals & Chemical
Non-Metallic Mineral products
Basic Metals. Alloys &
Wood & Wood Products
Paper & Paper Products
Leather & Leather Products xi)
Machinery & Machine tools
Transport Equipment & parts
The classification of „manufactured products‟ is similar to the classification adopted in the Index
of Industrial Production (IIP) except that the sub group of „Other Manufacturing „ has not been
retained and its traded value has been imputed in to remaining sub-groups.
8) Methodology of Index Calculation
Actual index compilation is done in stages, though due to computerization now, the machines do
all complex calculations. In the first stage, once the price data are scrutinized, price relative for
each price quote is calculated. Price relative is calculated as the ratio of the current price to the
base price multiplied by 100 i.e. (P1/Po)X100. Assigning weights at quotations level is difficult,
as it needs detailed data.
In the next stage, commodity/item level index is arrived at as the simple arithmetic average of
the price relatives of all the varieties (each quote) included under that commodity. An average of
price ratio/ relative is used under implicit assumption that each price quotation collected for an
item/commodity index compilation has equal importance i.e. the shares of production value is
equal. Where as if the ratio of average prices is adopted instead, the implicit assumption would
be that importance of each price quotation depends on its price level in the base period and all
the quantities produced are equal. Since quantities produced at unit level are not equal the
average of price relatives method is preferred to arrive at item level index in WPI.
Next, the indices for the sub groups/groups/ major groups are compiled and the aggregation
method is based on Laspeyres formula as below:
I= S (Ii x Wi) / S Wi
I = Index numbers of wholesale prices of a sub- group/group/ major group/ all commodities
S = represents the summation operation,
Ii = Index of the ith item / sub- group/ group/ major group.
Wi = Weight assigned to the ith item of sub- group/group/ major group.
The weights are value weights. Aggregation is first done at sub-group and group level. All
commodities index is compiled by aggregating Major group indices.
9) Handling of the Seasonal Commodities :
There are number of agriculture items, especially some fruits and vegetables, which are of
seasonal nature. When a particular seasonal item disappears from the market and its prices are
not available because of its being out of season, the weights of such item is imputed amongst the
other items on pro rata basis with in the sub-group of vegetables or fruits. The underlying
assumption is that if the items remained available, the prices of these items would have moved in
the same proportion as the prices of the other items in the sub-group, which did remain available.
This is equivalent to giving a greater weight to the remaining items. The seasonality problem can
be sorted by adopting other methods like, i) prices of unavailable items can also be extrapolated
forward from the period of availability or ii) if such seasonal item has insignificant weight it can
be taken permanently from the basket etc.
10) Procedure for Estimation for Non-response and Data Substitution
As the series grow older, many of the items in the basket tend to disappear from the market, or
item specification may change or the source agency may no longer manufacture the item.
If the source agency stops manufacturing and the item is still available in the
market, then efforts are made to locate and fix another representative source producing item with
In case no suitable substitute is available, the weight of the item is imputed
to similar other item or among other items of the sub-group/group. The criterion for imputation is
that the price movement of the outgoing item and the item to which weight is imputed is similar.
Imputation of weight is not a long-term solution and ultimately replacement has to be effected.
In case item with different specifications need to be taken in the basket as a
substitute then the new price and old price is linked by splicing.
Substitution and replacement: First of all it should be ensured that the prices of both the price
quotations, outgoing quotation (old price) and incoming quotation (new price) are collected
concurrently for some time and respective price movements observed for any extreme variation.
Splicing is done by working out a ratio (linking coefficient) of concurrent price quotations and
multiplied by the base price as below:
Price of New Quotation (Incoming Price)
-----------------------------------------------------X Base Price of the item
Price of old quotation (Outgoing Price)
Price relatives are worked out by dividing the current price with the updated base price. Splicing
can be done other way round, wherein, linking coefficient can be worked out by dividing old
price (outgoing quote) with the new price (incoming quote) and multiplied by the current price.
In WPI the substitution is effected from the date final indices are compiled. The effective date
and the splicing ratio are documented properly.
11) Provisional Vs Final:
Primary objective of WPI is to bring out an estimate of headline inflation for the economy.
Because of late receipt of price data, part of the price data cannot be utilized as the WPI is
released on weekly basis. The weekly indices are compiled after a short gap of two weeks only
as compared to other indices, which are compiled on monthly basis. The WPI are, therefore
released provisionally and final revised indices, incorporating all possible quotations, are
released after a gap of two months.
12) Data collection mechanism :
At present data collection for WPI is solely based on voluntary basis. Price data pertaining to
„Primary articles‟ and „Fuel & petroleum products‟ are mainly collected through administrative
Ministries/Departments, PSUs and state government Departments. For „Manufactured products‟,
apart from some government sources, data collection is done through Chambers of Commerce,
Trade Associations, Business Houses and leading Manufacturing Units.
13) Linking Factor:
In order to maintain continuity, the time series data on wholesale price index, it is important to
provide linking factor so that new series when released may be compared with the outgoing one.
It provides a basis for determination of cost escalation and wage settlement and secondly,
generates a long time series data for analytical purposes.
There are three commonly used methods for linking new series with old one i.e (i) arithmetic
conversion method (ii) ratio method and (iii) regression method. In arithmetic linking method the
relationship between the indices in the old series (y) and those in the new series (x) is assumed to
be linear i.e y = cx, where c is the conversion factor given by y
C = X , y and x being average values of the indices in the two series for the year chosen as the
base period (12 months) of the new series (in practice X =100). Under the ratio method, month
wise ratio of new indices and old indices are worked out first and then average of ratios is taken
as a linking factor. In the third method, the relationship is based on y = a+bx, where a and b
would be so estimated that the sum of squares of deviations of the actual values of y (during the
base year of the new series) from the estimated values (derived from the above equation) is
minimum. The linking factor derived from these three different formulae may vary and provide
different estimates. Therefore, it is necessary to analyze and assess the linking factor worked out
before these are released publicly. While publishing the linking factor, the option should be left
to the user to use any of these methods to suit their specific objectives.
The linking factor for the WPI, which has been published officially, has been based on arithmetic
conversion method. The linking factor is worked out only at aggregate level for all commodities.
Because of the vast changes in the commodity baskets, it has not been found feasible to compile
linking factor at group/ sub-group level. Even though for analytical purpose, it would be very
useful to have linking factor at desegregated level.
14) Approval and Release of revised Series
As per the established practice, a Working Group is set up for revision of existing WPI series
with the approval of the Minister in-charge of the Department of Industrial Policy & Promotion.
Detailed deliberations on all aspects including methodological issues are held first at the level of
sub groups and thereafter in the Working Group. The views expressed at both the levels and
recommendations based thereon are incorporated in the report of the Working Group.
The Report of the Working Group is first placed before the Technical Advisory Committee on
Statistics of Prices & Cost of Living (TAC on SPCL) in Central Statistical Organisation (CSO)
and thereafter before the Committee of Secretaries (COS). It is only after acceptance of the
report by the TAC on SPCL and its subsequent approval and appropriate direction of the COS;
the Office of the Economic Adviser through press release introduces the revised series of WPI.
15) Data Management and Dissemination System
The ultimate use of the index compilation will depend upon the quality of data management and
data dissemination. Though due to improved computer facilities it has now become easier to
compile, store and transmit WPI data. As SDDS norms of IMF are applicable to WPI, every
effort is made to ensure timeliness and transparency in release of the indices. Weekly WPI are
released to the press on every Friday. Dissemination of Weekly press release is also done
through official website simultaneously. Time series data are also made available to users
through print and electronic media on request. Report of the last Working Group is also placed
on the office website i.e. http://www.eaindustry.nic.in/