Only an economist would write Pay or Pray? The Impact of Charitable Subsidies on Religious Attendance:
I find strong evidence that religious giving and religious attendance are substitutes: larger subsidies to charitable giving lead to more religious giving, but less religious attendance, with an implied elasticity of attendance with respect to religious giving of -0.92. These results have important implications for the debate over charitable subsidies. They also serve to validate economic models of religious participation.
(Hat tip to Marginal Revolution.)