st: Censored repeated observations count data

[Paul GERRANS <p.gerrans@ecu.edu.au>]

Hello Statalisters,
I have a database which contains choice data of individuals drawn from three groups over a five year period.

Each choice shows how many investment options from an investment menu are used to contruct a portfolio. For example an individual in group one for the first 18 months has a choice of 5 options they can use in a portfolio choice. They can choose from one to five options in that portfolio choice. In two years time the number of options increases to 8 for that group and the individual could make another choice. With this one group there are four different periods over the five years (unequal) where the number of options available for a choice increases (3,8,12,14 options). The members of that group can make a choice multiple times in these periods. Similarly one other group has three different periods (again different length periods) where the number of options changes (5, 10,12,13). The third group has the same number of options over the whole period (6).

I am wanting to explain the number of options used in a choice as a functions of how many were available and the individual's characteristics. I assume I have to account for the censoring of the counts (which changes by group over time) and the different exposure time for an individual in each group to each sub-period. What would be the most appropriate approach in STATA?

Many thanks for any advice.
Paul

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