Hi Statalisters,

I am using -xtpoisson,fe- count data model to analyze my panel data. The dependent variable is the number of patents (npatent) and the independent variables include customer concentration (CC) and customer dependence (CD). The moderator is supplier-customer linked years (Linkage).

The full model should be: npatent=β0 + β1*CC + β2*CD + β3*Linkage + β4*(CC*Linkage) + β5*(CD*Linkage)+ controls + industry fixed effects + year fixed effects

When I run -xtpoisson,fe- regression with the full model, I see coefficients for CC and CD are both negative, -1.19 and -0.59, respectively.

Code:
xtpoisson npatent CC CDsum Linkage c.CC#c.Linkage c.CDsum#c.Linkage $controls i.SIC2N i.fyear, fe

Array


However, when I run the -margins- for both CC and CD, I see coefficients turn to positive. These inconsistent coefficients make me confused about whether CC and CD are positive or negative signals of the dependent variables.

Code:
margins, at(CC=(0(0.1)0.6)) vsquish

Array



I am appreciated for any explanation and instruction about my data project.

BTW, I have read previous threads that argue about the function of -margins- in -xtpoisson,fe- settings. I just want to use -marginsplot- to better illustrate my interaction terms but find these inconsistent results by accident.

Thanks in advance.