"[W]hat factors might drive census participation? With the help of my colleague Charlotta Mellander, I decided to take a quick look. We examined the correlations between census participation and economic factors, demographic characteristics, and state personality traits. This analysis is based on simple correlations which identify associations between variables but do not specify causality. I also spoke to my colleague and collaborator, the Cambridge University personality psychologist Jason Rentfrow about these results.
The short answer is that in terms of who fills out census forms, personality is the only thing that seems to matter."
They looked at the predominant personality traits in states to see what impacts higher return rates. For example, states with high populations of extroverts were likely to have high rates of Census participation.