Hi all,

I'm trying to run the following code:

Code:
 ppmlhdfe died year `controls' if year!=2020, offset(ln_pop) absorb(facility)
My outcome is the number of people who died in a given facility in a given year, `controls' are facility-year varying covariates. When I run this code, I get a message saying that "year" is dropped because of collinearity with fixed effects. The problem is that when I run this without any other variables (no fixed effects, no controls) I still get a message that year is dropped due to collinearity. This doesn't happen if I run this using reghdfe or ppml without fixed effects. Note that I am able to run this model with year dummies (i.year) successfully!

Any ideas why this might be happening? There are 4 years of data, 129 facilities each year.