1. 2? 1? ?) are nonnegative for any ? ? ? ? * 12 = ? 23 . The rest of the proof of 2, about parameter conditions, is otherwise similar to that of Proposition 6. 22 We take the case ? 23 = ? ? 21 corresponding to situations where ? * 23 ? ? ? 21 : the second investment of the smaller firm occurs later under the tacit-collusion trigger than under the stand-alone trigger ? * 23 because the smaller firm delays its first investment beyond ? * 23 in order to collude;? ? ? * 12;This equilibrium exists if and only if both ? (1? 2? ?) ? ? (1? 2? ?) and ? (2? 1? ?) ? ? *
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