Since campaign contributions reveal the actor’s party leanings, they take place in a domain of social observation and are likely to be subject to social effects. We conducted a field experiment to identify some of these social effects. We sent letters to 92,000 contributors from all U.S....

We show how classic source-decomposition and subgroup-decomposition methods can be reconciled with regression methodology used in the recent literature. We also highlight some pitfalls that arise from uncritical use of the regression approach. The LIS database is used to compare the approaches...