I ran a regression with reghdfe on multiple imputation datasets, The data includes 500 organizations over 23 years, with 20 imputations.
I first estimated the regression using the vce(robust) then I re-ran the model using the option vce(cluster clustvar). In many cases, the standard errors were much smaller when I used the vce(cluster clustvar) option.

Does this seem reasonable? What can explain the difference between the cluster and the robust? Can this be caused because of the reghdfe absorb specification or the MI?

Code:

mi estimate, post cmdok:reghdfe f.women var1 var2 var3, absorb(id year) vce(robust)

mi estimate, post cmdok:reghdfe f.women var1 var2 var3, absorb(id year) vce(cluster id)


Thanks in advance!
Gayle