Hello,

I am estimating the following multilevel negative binomial model with an exposure term.

Code:
 menbreg surgery i.year##c.prop_race $covars, exposure(population) || countynum:, irr
In this model, surgery represents the number of surgeries, year is the year in which they were performed (2013-2016), prop_race is the proportion of a particular race in the county, population is the total population of the county, countynum is the county ID, and $covars is a set of county covariates.

1. After estimating this model, I would like to obtain the number of surgeries or their rates for counties at, say, the 25th percentile of prop_race for each year. How could I program this such that the code takes into account the exposure variable. Will I be able to interpret the output in counts of surgeries or as a rates? While I am not certain, I am thinking that the following code may help me get to some of it
Code:
 margins i.year, at(prop_race=(0.06))
if 0.06 is the value of prop_race at the 25th percentile.

2. Is there a way I could use the -predict- command to obtain numbers similar to what I will obtain from margins.

I am using Stata/MP 15.1. I have also looked through some previous discussions which examine margins after negative binomial models with exposure (not multilevel though), or after multilevel negative binomial models (but without the exposure term).

Thank you,
Caroline