  Will people eventually learn the value of an asset through observable
information? This paper studies observational learning in a market with
competitive prices. Comparing a market with public signals and a market with
private signals in a sequential trading model, we find that Pairwise
Informativeness (PI) is the sufficient and necessary learning condition for a
market with public signals; and Avery and Zemsky Condition (AZC) is the
sufficient and necessary learning condition for a market with private signals.
Moreover, when the number of states is 2 or 3, PI and AZC are equivalent. And
when the number of states is greater than 3, PI and Monotonic Likelihood Ratio
Property (MLRP) together imply asymptotic learning in the private signal case.
