Martin,
Many thanks for the stata.com presentations - I had not seen these
Michael E Roettger wrote:
Have you examined the distribution of the dependent variable?
If xtmepoisson fails to converge while xtpoisson converges, you make
have a distribution which does not fit the standard Poisson
distribution. Rabe-Hesketh and Skrondal (2008) note that xtpoisson
adjusts for overdispersion due to the way the individual-level random
effect is specified; xtpoisson also assumes that the random effect
has a log-gamma distribution.
If you have overdispersion, you might be able to use the xtgee
command, specifying that the dependent variable is a negative
binomial distribution. Dummy variables may also be added to control
for year effects.
I remain at the "Refining starting values:" so the delay does not seem
to be at convergence. Although the depvar is a little zero inflated si
I'll take a look at xtgee.
Many thanks
Simon
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