European Patents. Cincera (1997) performed count panel data regressions of patent activity using 181 international manufacturing firms investing substantial amounts in R\&D over the period 1983 to 1991. The dependent variable was the number of European patent applications filed by the firm in that year. This was regressed on current and 4 year lag of log of R\&D expenditures as well as \(\log\) of technological spillovers. Other control variables included the firm's geographical area as well as the firm's main industry sector. The data set can be downloaded from the Journal of Applied Econometrics archive web site.

(a) Replicate the descriptive statistics and correlation matrix given in Table I of Cincera (1997).

(b) Run the poisson and negative binomial regressions using robust variancecovariance matrices as described in equation (1) of Cincera (1997).

(c) Run xtpoisson and xtnbreg using both the fe and re options on this data. This should replicate the estimates (but not the standard errors), reported in column (3) of Table II of Cincera (1997) which is entitled conditional poisson.