I am trying to model growth over time for a number of companies (my unit of analysis). My dependent variable is a count (the number of acquisitions each firm made each year), and I'm having some trouble figuring out exactly how to model this. My assumption is that modeling the effect of time on this dependent variable with a linear model is inappropriate. Does anyone have any guidance regarding how to model such a dependent variable such that I could include both random and fixed effects? Thanks in advance. S. Trevis Certo, PhD Assistant Professor & Mays Research Fellow Management Department Mays Business School Texas A&M University [[alternative HTML version deleted]]
Certo, Trevis wrote:> I am trying to model growth over time for a number of companies (my unit > of analysis). My dependent variable is a count (the number of > acquisitions each firm made each year), and I'm having some trouble > figuring out exactly how to model this. My assumption is that modeling > the effect of time on this dependent variable with a linear model is > inappropriate. Does anyone have any guidance regarding how to model such > a dependent variable such that I could include both random and fixed > effects? Thanks in advance.You may want to consider a generalized linear mixed model (GLMM) for the Poisson family. These can be fit with the GLMM function in the lme4 package.