I have an unbalanced panel of entry by firms into various towns (M=1123) in
a particular industry in the US during the period 1969-1976. The number of
firms that enter each town during each year varies from 0 to 39. Two
different types of firms enter: (a) those who sell technologically
sophisticated products, and (b) those who sell technologically inferior
products. The variable SUPTECH denotes the number of firms which offer
technologically superior products while INFTECH DENOTES those supplying
technologically inferior products. The data structure looks like this:
In addition there are a number of other independent variables such volume of
sales in each town (market size), demographics, and so on. I am testing
several hypotheses concerning the nature of entry. However, my query to
statalisters is a simple one.
I am testing whether the probability of entry of firms offering inferior
technology products increases with the number of firms. I use an ordered
probit model for this where the dependent variable is INFTECH (0 to 14).
However, since I have a panel data could I also use a mixed model?
