Incentive Effect of Piece-Rate Contracts: Evidence from Two Small Field Experiments

We conducted two field experiments in a tree-thinning setting. In one experiment, we switched the pay of a randomly chosen half (the treatment group) from hourly wages to piece-rate pay. Workers in the control group were paid hourly wages throughout. In the second experiment, workers were switched from hourly to piece-rate pay all at once. The difference-in-difference and before-after estimates suggest that the productivity increase was on the order of 20-23 percent. Although the sample size is small, the estimates are statistically significant and robust. While the quality did not drop, the study highlights the measurement costs in setting up the right level of piece rates. We also discuss the strengths and weaknesses of using randomized control (and treatment) groups or not in conducting field experiments within firms.