Euler’s theorem
Homogeneous Function
),,,(
0wherenumberanyfor
if,degreeofshomogeneouisfunctionA
21
21
n
k
n
sxsxsxfYs
ss
k),x,,xf(xy


=
>
=
[Euler’s Theorem]
 Homogeneity of degree 1 is often
called linear homogeneity.
 An important property of
homogeneous functions is given by
Euler’s Theorem.
Euler’s Theorem
argument.ithits
respect toithfunction wtheofderivativepartialtheis
where,valuesofsetanyfor
,degreeofshomogeneouisthat
functiontemultivariaanyFor
2121
212111
21
),x,,x(xf),x,,x(x
),x,,x(xfx),x,,x(xfxky
k
),x,,xf(xy
nin
nnnn
n



++=
=
Proof Euler’s Theorem
.degreeofshomogeneouisfunctionoriginalthen the
true,isabovetheIfholds.theoremthisofconverseThe
),,,(),,,(
TheoremsEuler'getwe,Letting
),,,(),,,(
respect towithabovetheofderivativepartialtheTake
),,,(functionshomogeneouDefinition
212111
212111
1
21
k
xxxfxxxxfxky
1s
sxsxsxfxsxsxsxfxyks
s
sxsxsxfys
nnnn
nnnn
k
n
K



++=
=
++=
=
−
Division of National Income
( )[ ] ( )
[ ]
( )YYwLrKYHence
YKLKK
K
Y
rKand
YLLKL
L
Y
wL
L
L
Y
K
K
Y
LKY
ββ
ββα
βαβ
α
ββ
ββ
ββ
−+=+=
==
∂
∂
=
−=−=
∂
∂
=
∂
∂
+
∂
∂
=
=
−−
−
−
1,
.
11
impliesThiswage.realandreturnreally theirrespective
paidarelaborandcapitaln,competitioperfectunderNow
Y
therefore1,degreeofshomogeneouiswhich
isfunctionproductionnationalthat theSuppose
11
1
Properties of Marginal
Products
( )
( ) ( )
β
β
βα
αβ






−=−=
∂
∂






==
∂
∂
−=
∂
∂
=
∂
∂
−
−
−−
−
−−
L
K
LαKβ
L
Y
and
K
L
LβαK
K
Y
LαKβ
L
Y
LβαK
K
Y
ββ
ββ
ββ
ββ
11
asproductsmarginalthecan writeWe.1
Labor,ofproductmarginalfor theLikewise
zero.degreeofshomogeneouiswhich
function,productionaccountingincomenationalourFor
1
11
11
Arguments of Functions that are
Homogeneous degree zero
QED
x
x
x
x
x
x
f),x,,x,,xf(x
then
x
sLet
),sx,,sx,,sxf(sx),x,,x,,xf(xs
nianyfor
x
x
x
x
x
x
f
),x,,x,,xf(x
i
n
ii
ni
i
nini
i
n
ii
ni






=
=
=
=





,,1,,,
,
1
0,degreeofshomogeneouisfunctiontheSince:Proof
.,...,2,1,,1,,,
aswrittenbecanzerodegreeof
shomogeneouisthatfunctionAny
21
21
2121
0
21
21




First Partial Derivatives of
Homogeneous Functions
( )
( )
.degreeof
shomogeneouisn,,1,2,ianyfor
,,,
sderivativepartialfirstistsofeachthen
,degreeofshomogeneouis,,,function,theIf
21
21
k-1
x
xxxf
f
kxxxf
i
n
i
n



=
∂
∂
=
Proof of previous slide
( ) ( )
( ) ( )
( )
( )
( )
( ) ( )
( ) ( )
( ) ( )
.degreeofshomogeneouisderivativetheimpliesWhich
,,,,,,
,,,,,,
equaltwothesetting,,,
,,,
,,,
,,,,,,
,,,,,,
21
1
21
2121
21
21
21
2121
2121
k-1
xxxfssxsxsxf
orxxxfssxsxsxsf
xxxfs
x
xxxfs
andsxsxsxsf
dx
sxd
sx
sxsxsxf
x
sxsxsxf
xxxfssxsxsxfknowWe
ni
k
ni
ni
k
ni
ni
k
i
n
k
ni
i
i
i
n
i
n
n
k
n







−
=
=
=
∂
∂
=
⋅
∂
∂
=
∂
∂
=
Homothetic function
.allfor0iforallfor0is
thatmonotonic,strictlyisfunctiontheiffunction
homotheticaisthenfunction,shomogeneou
aisifThisfunctin.shomogeneoua
ofationtransformmontonicaisfunctionhomotheticA
21
yg'(y)yg'(y)
g(y)
g(y)z
),x,,xf(xy n
<>
=
= 
Example homothetic function
( )
( )
s.homogeneouarefunctionshomotheticallnot
,homotheticarefunctionsshomogeneouwhileTherefore,
?.degree
ofshomogeneouisfunctionoriginalarenexcept whe
)ln(
)ln()ln()ln()ln()ln(
)ln()ln(lnLet
.degreeofshomogeneouiswhich
wssw
szxszsxnow
zx(y)w
zxylet
k
≠++=
+++=+
+==
+=
βα
βαβαβα
βα
βαβα

euler's theorem

  • 1.
  • 2.
    Homogeneous Function ),,,( 0wherenumberanyfor if,degreeofshomogeneouisfunctionA 21 21 n k n sxsxsxfYs ss k),x,,xf(xy   = > = [Euler’s Theorem] Homogeneity of degree 1 is often called linear homogeneity.  An important property of homogeneous functions is given by Euler’s Theorem.
  • 3.
    Euler’s Theorem argument.ithits respect toithfunctionwtheofderivativepartialtheis where,valuesofsetanyfor ,degreeofshomogeneouisthat functiontemultivariaanyFor 2121 212111 21 ),x,,x(xf),x,,x(x ),x,,x(xfx),x,,x(xfxky k ),x,,xf(xy nin nnnn n    ++= =
  • 4.
    Proof Euler’s Theorem .degreeofshomogeneouisfunctionoriginalthenthe true,isabovetheIfholds.theoremthisofconverseThe ),,,(),,,( TheoremsEuler'getwe,Letting ),,,(),,,( respect towithabovetheofderivativepartialtheTake ),,,(functionshomogeneouDefinition 212111 212111 1 21 k xxxfxxxxfxky 1s sxsxsxfxsxsxsxfxyks s sxsxsxfys nnnn nnnn k n K    ++= = ++= = −
  • 5.
    Division of NationalIncome ( )[ ] ( ) [ ] ( )YYwLrKYHence YKLKK K Y rKand YLLKL L Y wL L L Y K K Y LKY ββ ββα βαβ α ββ ββ ββ −+=+= == ∂ ∂ = −=−= ∂ ∂ = ∂ ∂ + ∂ ∂ = = −− − − 1, . 11 impliesThiswage.realandreturnreally theirrespective paidarelaborandcapitaln,competitioperfectunderNow Y therefore1,degreeofshomogeneouiswhich isfunctionproductionnationalthat theSuppose 11 1
  • 6.
    Properties of Marginal Products () ( ) ( ) β β βα αβ       −=−= ∂ ∂       == ∂ ∂ −= ∂ ∂ = ∂ ∂ − − −− − −− L K LαKβ L Y and K L LβαK K Y LαKβ L Y LβαK K Y ββ ββ ββ ββ 11 asproductsmarginalthecan writeWe.1 Labor,ofproductmarginalfor theLikewise zero.degreeofshomogeneouiswhich function,productionaccountingincomenationalourFor 1 11 11
  • 7.
    Arguments of Functionsthat are Homogeneous degree zero QED x x x x x x f),x,,x,,xf(x then x sLet ),sx,,sx,,sxf(sx),x,,x,,xf(xs nianyfor x x x x x x f ),x,,x,,xf(x i n ii ni i nini i n ii ni       = = = =      ,,1,,, , 1 0,degreeofshomogeneouisfunctiontheSince:Proof .,...,2,1,,1,,, aswrittenbecanzerodegreeof shomogeneouisthatfunctionAny 21 21 2121 0 21 21    
  • 8.
    First Partial Derivativesof Homogeneous Functions ( ) ( ) .degreeof shomogeneouisn,,1,2,ianyfor ,,, sderivativepartialfirstistsofeachthen ,degreeofshomogeneouis,,,function,theIf 21 21 k-1 x xxxf f kxxxf i n i n    = ∂ ∂ =
  • 9.
    Proof of previousslide ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) .degreeofshomogeneouisderivativetheimpliesWhich ,,,,,, ,,,,,, equaltwothesetting,,, ,,, ,,, ,,,,,, ,,,,,, 21 1 21 2121 21 21 21 2121 2121 k-1 xxxfssxsxsxf orxxxfssxsxsxsf xxxfs x xxxfs andsxsxsxsf dx sxd sx sxsxsxf x sxsxsxf xxxfssxsxsxfknowWe ni k ni ni k ni ni k i n k ni i i i n i n n k n        − = = = ∂ ∂ = ⋅ ∂ ∂ = ∂ ∂ =
  • 10.
  • 11.
    Example homothetic function () ( ) s.homogeneouarefunctionshomotheticallnot ,homotheticarefunctionsshomogeneouwhileTherefore, ?.degree ofshomogeneouisfunctionoriginalarenexcept whe )ln( )ln()ln()ln()ln()ln( )ln()ln(lnLet .degreeofshomogeneouiswhich wssw szxszsxnow zx(y)w zxylet k ≠++= +++=+ +== += βα βαβαβα βα βαβα