To date, the political trust literature has been bifurcated along micro-macro lines. Some scholars have studied differences in political trust across individuals, while others have studied aggregate political trust levels over time. In this paper, I propose a micro-macro model that joins the two. I use the model and data from the 1958-2008 American National Election Studies to examine the effects of incumbent, economic and policy assessments on individual political trust and on political trust over time.The results show that although economic and policy assessments impact individuallevel political trust, they do not explain the more general trend. Assessments of incumbents, however, explain both. I argue that studies of political trust need to pay greater attention to the distinction between effect, mean and compositional changes. Only those predictors that exhibit the latter two can usefully explain why political trust changes over time. The paper concludes with a discussion of the utility of the micromacro approach for the study of political and other forms of trust.