Julian,

  A McFadden's R2 (1-full model ll/constant only ll) could be easily computed as follows (using the "fish" data).

--begin syntax--

webuse fish

hplogit count persons livebait camper child

scalar full_model = e(ll)

hplogit count

scalar constant_model = e(ll)

scalar mcfadden_r2 = 1-scalar(full_model)/scalar(constant_model)

display scalar(mcfadden_r2)

--end syntax--

If you have access to a Stata version that can estimate a Zero Inflated Poisson and download the r2c module you will find that it provides a similar answer for a similar model

--begin syntax--

webuse fish

zip count persons livebait camper child , inflate(persons livebait camper child)

r2c

--end syntax--

- joe

Data R2C: Stata module to compute several fit statistics for coun...

thanks