Appendix
Proof of Proposition 1. As in Diamond (1980), the Lagrangian associated with the opti-
mal tax problem is
L(c(n), b, λ; r) =
n∙n p
nm
`n
+λ
∙m* (c(n),b,r)
u
m(n)
ρm(n)
(c(n), m)f (m, n)dm +
m* (c(n),b,r)
-m*(c(n),b,r)
m(n)
u(b, r)f (m, n)dm dn
(A.1)
ρm(n)
[n - c(n)]f (m, n)dm -
m* (c(n),b,r)
bf (m, n)dm dn - R
The first-order condition with respect to c (n) yields:
∙m(n)
1—
1 ∂u (c (n) , m)
m*(c(n),b,r) _
= [n - c(n) + b]
λ ∂c (n)
∂m* (c (n) , b, r)
∂c (n)
f(m, n)dm
f (m*,n).
(A.2)
Using (5) and (6), and dividing both sides by F(m*,n), (A.2) can be rewritten as
1 „М -WWdm* (c(n) ,b,r) f (m*,n)
(A.3)
1 - g(n) = τ (n) ■ Fm ■
From (A.3) we see that τ(n) takes the sign of 1 - g(n) as stated in Proposition 1.
The first-order condition with respect to r is
≤0 ≤ 0, r ≥ 0 and r-τf- = 0.
∂r ∂r
(A.4)
Differentiating (A.1) yields:
∂L ∂u (b, r)
∂r ∂r
+λ Z
n n
?n pm(n)
f(m, n)dmdn
Jn Jm*(c(n),b,r)
n dm* (c (n) ,b,r) A∣AW∕* W
----------------[n — c (n) + b] f (m , n)dn.
∂r
(A.5)
By the Envelope Theorem, (A.5) provides the dW/dr that we display in (8).
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