Hello,

I have a regression of the form: xtreg yvariable c.xvariable#i.year c.xvariable i.year `control', fe

where years are 1999, 2002, 2006, 2010 and 2014. When I run the regression, the coefficients in the interaction term "c.xvariable#i.year" for years 2002, 2006 and 2014 are omitted because of collinearity. However, those years do show coefficients in the "i.year" fixed effects part. Is there something I am doing wrong? Should I not include the variable "year" both in "c.xvariable#i.year" and by itself in "i.year"?

My goal is to understand the impact that xvariable has on yvariable broken down by year, the calculation for 2014 for example should be=c.xvariable+2014.year#c.xvariable" right? Or do I have to add the coefficients of "2014.year" too?

Thank you very much,

Joan