Euler's Theorem
Eulers Theorem states that if we have a function which is homogeneous of degree 1 (e.g. constant returns to scale, if a production function), then we can express it as the sum of its arguments weighted by their first partial derivatives.
Definition: (Linear Homogeneity) Let ヲ :Rn ョ R be a real-valued function. Then we say ヲ (x1, x2 ...., xn) is homogeneous of degree one or linearly homogeneous if lヲ(x) = ヲ (lx) where l ウ 0 (x is the vector [x1...xn]).
Theorem: (Euler's Theorem) If the function ヲ :Rn ョ R is linearly homogeneous of degree 1 then:
ヲ(x1, x2, ...., xn) = x1キ[カヲ/カx1] + x2キ [カヲ/カ x2] + ...... + xnキ[カヲ /dカxn]
or simply:
ヲ(x) = ・/font>i=1n [カヲ (x)/カxi]キxi
There is a corollary to this:
.Corollary: if ヲ :Rn ョ R is homogenous of degree 1, then:
・/font> ni=1[カ2ヲ(x)/カ xiカxj]xi = 0 for any j.
For proofs, see our mathematical section.