Deep or aggregate habit formation? Evidence from a new-Keynesian business cycle model

Habit formation is a fixture of contemporary new-Keynesian models. The vast majority assume that agents form habits strictly over consumption of an aggregate good, leaving open the question of whether it might be preferable to have them form habits over differentiated products instead–an arrangement known as deep habits. I answer this question by estimating a model that nests both habit concepts as special cases. Estimates reveal that the data favor a specification in which consumption habits are stronger at the product level than at the aggregate level. A mix of significance tests and simulation results indicate that including deep habits greatly improves model fit, most notably with regard to inflation dynamics.