Score contribution per author:
α: calibrated so average coauthorship-adjusted count equals average raw count
Experimental economists currently lack a convention for how to pay subjects in experiments with multiple tasks. We provide a theoretical framework for analyzing this question. Assuming statewise monotonicity and nothing else, we prove that paying for one randomly chosen problem--the random problem selection mechanism--is essentially the only incentive compatible mechanism. Paying for every period is similarly justified when we assume only a "no complementarities at the top" condition. To help experimenters decide which is appropriate for their particular experiment, we discuss empirical tests of these two assumptions.