In a Herd? Herding with costly observation and an unknown number of predecessors

We consider a sequential decision to adopt/not adopt a technology in a herding environment with costly observation. The novelty compared to the previous models on herding with costly observation, such as Kultti and Miettinen (2006a), is that the agents do not know how many other agents have been in the same situation earlier. It turns out that herding no longer arises deterministically. We show that when observation costs are low there exists a unique symmetric pure strategy equilibrium where all agents observe the actions of two immediate predecessors in order to find out whether they are in a herd or not.