equilibrium characterized in the Proposition 1 is unique in the class of Markov
perfect equilibria.
We will demonstate the uniqueness of continuation values for every state
j. For given state-contingent continuation values we have already argued that
the problem reduces to a standard all-pay auction for both players at each in-
terior state. Hence, uniqueness results from the uniqueness of the equilibrium
in the standard two-player all-pay auction with complete information.
Our proof will start by assuming that m > 3 and j0 ∈ {2,...m — 1}. (The
case of m = 2 corresponds trivially to the all-pay auction.) We claim the
following:
Claim 8 In any Markov perfect equilibrium, for all к ≤ j0 — 1, vb (к) = 0
and for all к ≤ j0 — 2, va(^ = δkZa.
Proof. At к = 0 by construction va(0) = Za and vb (0) = 0, so the claim
holds for к = 0. Since Za > Zb and m > 3, from (9) evaluated at к = 2
it follows that J(0) = Za > max(S2ZA,Sm-2ZB) > va(2) + vb(2) = J(2).
Hence from (i) za(1) > zb(I) and from (3) and (4) va(1) = 5[Za — vb(2)]
and vb(1) = 0. It immediately follows that J(1) = 5[Za — vb(2)]. This
implies that the claim holds when j0 = 2, which by definition of j0 implies
that m = 3.
So assume that j0 ∈ {3,...m — 1}. We will now prove the claim by
induction on к. Suppose that for some к, 1 ≤ к ≤ j0 — 2, vb(Z) = 0 for all
I ≤ к and Va(Z) = S1Za for all Z ≤ к — 1. (Note that the supposition holds
for к = 1) We claim that va^) = SkZa and vb(к + 1) = 0.
To demonstrate this observe that by (5)
va(^ = Sva^ + 1) + max(0,S[(vA^ —1)+ Vb (к —1)) — (va (к + 1)+ Vb (к + 1))])
Since Vb(к) = 0, by (6) Zb(к) — za(^ = S[(va^ + 1) + Vb(к + 1)) —
(vA(k — 1) + vb(к — 1))] ≤ 0, which implies by (iii') that
1>А(к) = %(к — 1) + Vb (к — 1)) — Vb (к + 1)] = 4'>l 1Z l. — Vb (к + 1)]
Moreover, vb(к + 1) = Svb(к) + Smax(0, (va^ + 2)+ vb(к + 2)) — ^А(к) +
Vb(к))) = Smax(0, (va (к + 2) + Vb(к + 2)) — S[Sk-1ZA — Vb(к + 1)]).
Suppose by way of contradiction that vb (к + 1) > 0. Then vb (к + 1) =
S[va^ + 2) + vb(к + 2) — S(Sk-1Za) + Svb(к + 1)] > 0,which implies that
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