limitations of the frequently used specification test that distinguishes between the standard models of pure and impure altruism … impure altruism compared with pure altruism, we show that, in general, it can be either more or less. Second, we propose a … heterogeneity based on park and volunteer hour types, are theoretically consistent with the mainstay model of impure altruism …

? Previous models of altruism that focus on the overall impact of a gift cannot rationalize this behavior, despite its prevalence …