We consider a sequential decision model in which entrepreneurs decide
on whether to enter a potential new market. Individual entrepreneurs h
ave private expectations about the new market's viability. Over time,
they learn about its viability from their own experience as well as th
at of earlier entrepreneurs. The distribution of the private expectati
ons is said to be heterogeneous if external prior beliefs about the ma
rket's viability exist. We show that heterogeneity of expectations cut
s both ways: while it facilitates the birth of viable markets, it also
generates, via the existence of extremal beliefs, 'excessive' entry i
n non-viable markets.