N ɪ NN N
In C (p,u) = α0 + J2"iln Pi + Ô Σ ∑7 *jln piln Pj + "’0 Π∑l , (27)
ù
i=l i=l j=l
i=l
which is homogeneous of degree one in prices p if the following parameter
restrictions hold:
N |
N Σ^ i = 0, |
(28) |
i=l |
i=l | |
N |
N | |
∑7 ↑i = 0 V7. |
∑7 *j = 0 v<, |
(29) |
i=l |
j=l | |
_ * 7 *j = |
* .* 7ji∙ |
(30) |
By multiplying both sides of Shephard’s Lemma ∂c (p,u) ∕∂pi = qi with
Pi∕c (p,u) we get
∂ ln c (p,u)
ln Pi
Piqi
c (p,u)
(31)
so that we can derive a budget share equation from (31):
N N
wi = ai + 7ijlnPj + βiuβо ∏ Pi1 ∙ (32)
j=l i=l
As for a utilitiy maximizing household C (p,u) = M, we can derive the
utiltiy level u via the indirect utility function:
l ш ln c (p,u) — ln a (p)
(33)
v (p,M) = 1 м ∖—i---^TΓ = u∙
ln о (p) — ln a (p)
Putting the utiltiy level u from equation (33) in (32), we get the common
AIDS budget share equation:
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