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Measuring the cost of nutritious diets

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Will Masters, Tufts University
Expert consultation on trade and nutrition
15-16 November 2016, FAO Headquarters, Rome
http://www.fao.org/economic/est/est-events-new/tradenutrition/en/

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Measuring the cost of nutritious diets

  1. 1. Measuring the cost of nutritious diets: Results for diet diversity in Ghana and Tanzania Will Masters Friedman School of Nutrition Science & Policy, Tufts University www.nutrition.tufts.edu | http://sites.tufts.edu/willmasters Presentation at the FAO Expert Consultation on Trade and Nutrition 15-16 November 2016
  2. 2. New price indexes • Indicators of Affordability of Nutritious Diets in Africa (IANDA) – Project funded by UKAid through its program on Innovative Methods and Metrics for Ag-Nutrition Actions (IMMANA), managed by LCIRAH (LSHTM, SOAS) and Tufts University – Project led by Jennie Coates and Anna Herforth, with Rebecca Heidkamp (Johns Hopkins University), Daniel Sarpong (University of Ghana), Fulgence Mishili and Joyce Kinabo (Sokoine University) – Today’s results are with Yan Bai (PhD student at Tufts) Measuring the cost of nutritious diets in Africa motivation | method | ghana | tanzania | next steps
  3. 3. But is nutritious food also becoming less expensive? Measuring the cost of nutritious diets in Africa motivation | method | ghana | tanzania | next steps What do food price indexes tell us about the cost of nutritious diets?
  4. 4. Measuring the cost of nutritious diets in Africa motivation | method | ghana | tanzania | next steps Existing food price indexes are weighted by market value The FAO Food Price Index is a measure of the monthly change in international prices of a basket of food commodities. It consists of the average of five commodity group price indices, weighted with the average export shares of each of the groups for 2002-2004. Total of 23 commodities (73 prices), in 5 groups: • Cereals -- wheat (11), maize (1), rice (16) • Oils/Fats -- soybean, sunflower, rapeseed, groundnut, cottonseed, copra, palm kernel, palm, linseed, castor (1 each) • Dairy -- whole milk powder, skim milk powder, cheese (2 each), cheese (1) • Meat -- poultry (13), beef (7), pork (6), sheep (1) • Sugar -- sugar (1) To measure “world prices”, the FAO aims to include traded foods
  5. 5. Measuring the cost of nutritious diets in Africa motivation | method | ghana | tanzania | next steps Food price trends and fluctuations differ by level of value added To measure cost of living (or output), national accounts aim to include all goods & services Food away from home Food at home Processed food & feed Unprocessed food and feed Source: US. Bureau of Labor Statistics, downloaded 12 November 2016. Definitions and chart data are available at http://myf.re/g/aPV1 Consumer price indexes, weighted by expenditure shares Producer price indexes, weighted by market sales
  6. 6. Measuring the cost of nutritious diets in Africa motivation | method | ghana | tanzania | next steps What is the cost of a nutritious diet? • Need nutritional values, rather than market values – Previous subsistence indexes focus on dietary energy • undernourishment, to maintain weight and physical activity cost of staple foods or calories – Today will focus on cost of dietary diversity • beyond staples, foods with more nutrients and other attributes => cost of specific foods or food groups – Next step will be cost of nutrient adequacy • account for quantities, to reach recommended dietary intake => cost of nutrients – Then include cost of other healthful or harmful attributes • dietary guidelines, with upper as well as lower limits => cost of attributes (+ for beneficial, - for harmful)
  7. 7. Measuring the cost of nutritious diets in Africa motivation | method | ghana | tanzania | next steps Possible indexes of nutritional value • For hunger and dietary energy, a long history and wide use – Playfair (1821) chart of wheat prices and wages for 1565 to 1821 – Sukhatme (1961) and FAO’s Prevalence of Undernourishment in calories – Drewnowski (2004) measure of energy cost ($/kcal) and density (kcal/kg) • For nutrient adequacy, a long history and many specific uses – Stigler (1945) linear programming to compute least-cost diets – USDA Thrifty Food Plan for US nutrition assistance (1975, 1983, 1999, 2006) – SCUK Cost of Diet tool (2009) and FANTA et al. Optifood (2012) for aid programs • But diet diversity in terms of food groups of particular interest today – DD takes account of all attributes in each food group, not just nutrients – Grouping foods by attributes facilitates dietary surveys, where frequency of intake over 24hr (or 7d) is feasible to recall, whereas quantities are usually unknown – Number of food groups included in the diet has been linked to child height (Arimond & Ruel 2004) and to women’s nutrient adequacy (Arimond et al. 2010)
  8. 8. Measuring the cost of nutritious diets in Africa motivation | method | ghana | tanzania | next steps Dietary diversity has overtaken nutrients in popularity among nutritionists Source: Calculated from https://books.google.com/ngrams, 12 November 2016 Relative frequency of use in English-language books, 1950-2008
  9. 9. Measuring the cost of nutritious diets in Africa motivation | method | ghana | tanzania | next steps Definitions of dietary diversity • DD measures have evolved rapidly in recent years – Nonlinearity in response • From number of food groups (DDS) to minimum thresholds (MDD) – Nonunitary households • From household scores (HDDS) to individuals (children 0-5, women 15-49) • Focus now is on Minimum Dietary Diversity for Women (MDD-W) – Defined as eating at least 5 out of 10 food groups in previous 24 hrs • Starchy staples (Grains, white roots/tubers, plantains) • Pulses (beans, peas and lentils – includes soybeans) • Nuts and seeds (higher fat than pulses, includes groundnuts) • Meat, poultry and fish • Dark green leafy vegetables • Other vitA-rich fruits & vegetables • Other vegetables • Other fruits • Eggs • Dairy
  10. 10. Measuring the cost of nutritious diets in Africa motivation | method | ghana | tanzania | next steps Interpretation of dietary diversity • MDD-W is primarily seen as a validated proxy for nutrient adequacy – DD might also protect against excess intake of some foods – DD can also be seen as a measure of real income and well-being • MDD-W has a direct economic interpretation – Within groups, all foods are perfect substitutes – Each group provides a different mix of attributes – Every group also contributes towards energy balance – Groups can be ranked by cost towards total daily energy needed – The least costly energy source (typically starchy staples) can meet few other needs – People will include higher-cost energy sources in their diet to meet additional needs – People who include at least five groups are likely to reach adequacy thresholds • MDD-W food groups reflect common dietary substitutions • Low-cost starchy staples: Grains, white roots/tubers, plantains • Plant-based protein & fat: Pulses; Nuts and seeds • Animal-sourced foods: Eggs; Dairy; Meat, poultry and fish • Micronutrient-rich foods: Dark green leafy vegetables, Other vitamin A-rich fruits & vegetables Other vegetables, Other fruits
  11. 11. Measuring the cost of nutritious diets in Africa motivation | method | ghana | tanzania | next steps Computing the cost of dietary diversity 1.Obtain market prices -- today’s data are from national statistical offices (prices collected for national accounts, based on budget shares & uniformity) -- another source could be agricultural market information services (prices collected for market integration, based on role in long-distance trade or storage) -- eventually sources could include humanitarian agencies (prices collected for early warning (eg VAM), based on presence in remote markets) 2.Convert units of measure -- all prices deflated to 2011 PPP prices based on PWT 8.1 data -- quantities converted to dietary energy (kcal) or weight (kg) 3.Classify into MDD-W food groups -- select the one lowest-cost item in each group -- identify the fifth lowest-cost group
  12. 12. Results for Ghana Measuring the cost of nutritious diets in Africa motivation | method | ghana | tanzania | next steps • Monthly averages across multiple markets, Jan. 2005 – Dec. 2014 • No prices available for dark green leafy vegetables or dairy • The five lowest-cost are usually, in rank order: • Starchy staples: • Least costly is cassava or maize • Pulses • Least costly is usually soyabeans, occasionally cowpea • Nuts and seeds • Least costly is groundnuts • Vit A-rich fruits and vegetables • Least costly is mangoes, occasionally oranges, rarely tomatoes • Other fruit • Least costly is banana, occasionally pineapple • The higher-cost groups are usually: • Meat, poultry and fish • Least costly is usually smoked herring, occasionally salted dried tilapia • Other vegetables • Least costly is usually onions, occasionally garden eggs • Eggs • Usually the most expensive food group • Key questions: • Is it OK to use cost/kcal to reach energy needs, vs. cost/kg as meal ingredients? • Is it OK to count only five lowest-cost groups, vs. all food groups?
  13. 13. Measuring the cost of nutritious diets in Africa motivation | method | ghana | tanzania | next steps The least-cost starchy staple is usually cassava, but sometimes maize Sometimes maize can replace cassava Note: if we ranked foods by weight ($/kg), the least cost starchy staple would always be cassava
  14. 14. Measuring the cost of nutritious diets in Africa motivation | method | ghana | tanzania | next steps The least-cost vegetable is onions in season, otherwise garden eggs Note: if we ranked foods by weight ($/kg), the least cost other veg. would usually be garden eggs Garden eggs:
  15. 15. Measuring the cost of nutritious diets in Africa motivation | method | ghana | tanzania | next steps The least-cost fruit is almost always banana, and occasionally orange or pineapple Note: if we ranked foods by weight ($/kg), the least cost other fruit would usually be pineapple orange pineapple orange
  16. 16. Aggregating all food groups, fluctuations 2009-11 then rise 2012-14 Measuring the cost of nutritious diets in Africa motivation | method | ghana | tanzania | next steps The price of just one food from the 5th group The average of 8 foods, one from each group
  17. 17. We would get different results when ranking foods and food groups by weight Measuring the cost of nutritious diets in Africa motivation | method | ghana | tanzania | next steps When we choose the heaviest (least cost in $/kg) food from each group, the average of 8 foods is more stable and has a different trend
  18. 18. Results for Tanzania • Monthly averages across multiple markets, Jan. 2011 – Dec. 2015 • No prices available for dark green leafy vegetables or eggs • The five lowest-cost are usually, in rank order: • Starchy staples: • Least costly is always maize • Pulses • Least costly is always soyabeans • Nuts and seeds • Least costly is always groundnuts • Other fruits • Least costly is usually avocado, occasionally green banana • Meat, poultry and fish • Least costly is always pork meat • The higher-cost groups are usually: • Dairy • Least costly is fresh cow milk • Vit A-rich fruits and vegetables • Least costly is usually mangoes, sometimes papaya • Other vegetables • Least costly is onions • Key questions: • Is it OK to use cost/kcal to reach energy needs, vs. cost/kg as meal ingredients? • Is it OK to count only five lowest-cost groups, vs. all food groups? Measuring the cost of nutritious diets in Africa motivation | method | ghana | tanzania | next steps
  19. 19. Measuring the cost of nutritious diets in Africa motivation | method | ghana | tanzania | next steps The least costly VitA-rich fruit or vegetable is mangoes in season, otherwise papaya Papaya is occasionally less costly than mango
  20. 20. Measuring the cost of nutritious diets in Africa motivation | method | ghana | tanzania | next steps Aggregating across all food groups, rise in 2011-12 then relative stability to 2015 The price of just one food from the 5th group The average of 8 foods, one from each group
  21. 21. Measuring the cost of nutritious diets in Africa motivation | method | ghana | tanzania | next steps In the TZ data, the cost of the 5th group is far above the average of all 8 groups 012345 2011m1 2011m7 2012m1 2012m7 2013m1 2013m7 2014m1 2014m7 2015m1 2015m7 2016m1 Year/Month White Maize Grains Round Onions Green Banana Avocado Mangoes Papaya Fresh Cow Milk Soya Beans Groundnuts Pork Meat MCDD ACOG Figure 15. Minimium Prices by Foodstuffs and the MCDD/ACOG Indicators (per 1,000kcal) The average of 8 foods, one from each group Prices of the least-cost food in each group (energy basis)
  22. 22. Conclusions and next steps Measuring the cost of nutritious diets in Africa motivation | method | ghana | tanzania | next steps • Creating a price index for the cost of a nutritious diet is challenging – Need clear definition of “nutritious”: a quantity index • Here, we use MDD-W • Next, we will use RDIs • Eventually, include attributes other than nutrients – Need new kinds of data • Here, we use prices from GH & TZ national accounts • This is good enough for a pilot, not yet ready to guide policy or programs • Pilot reveals data-collection priorities – For this particular aspect of nutrition policy and programs » Missing groups: green leafy vegetables, dairy, eggs » Misfit definitions of groups: pulses vs. nuts/seeds » Misfit foods within groups: meat/fish/poultry (in TZ case) (For this index, would need least-cost item such as dried fish) – For this and many other uses in nutrition policy and programs » Food composition data, for items with market prices » Dietary intake data, to test how intake responds to prices
  23. 23. Conclusions and next steps (continued) Measuring the cost of nutritious diets in Africa motivation | method | ghana | tanzania | next steps • How can economists meet demand for cost-of-nutrition data? – Need new understanding of what a cost-of-nutrition index measures • Not a cost-of-living index! – A benchmark for least costly way to meet nutrition needs • Relevant to actual choices, but neither descriptive nor normative – Should fit only the envelope of actual behavior » How close a fit? (e.g. purchases by weight, or for culinary reasons) » Fit to whose needs? (what location, age/sex or other category) – Need clear agreement on definition of nutrition needs • So far we are focusing on MDD-W and RDIs, but… – may need to measures that count gains above/below clinical thresholds – may need measures of other attributes beyond energy & nutrients => a long and complex research agenda !
  24. 24. Data analysis: Yan Bai (PhD student) Data sourcing: Daniel Sarpong (Ghana) Fulgence Mishili (Tanzania) Project leadership: Jennie Coates (PI) Anna Herforth (Co-PI) Rebecca Heidkamp (JHU) Joyce Kinabo (Sokoine) Funding: DFID, through IMMANA Thank you!

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