Pay It Backward: Per-Task Payments on Crowdsourcing Platforms Reduce Productivity.

Paid crowdsourcing marketplaces have gained popularity by using piecework, or payment for each microtask, to incentivize workers. This norm has remained relatively unchallenged. In this paper, we ask: is the pay-per-task method the right one? We draw on behavioral economic research to examine whether payment in bulk after every ten tasks, saving money via coupons instead of earning money, or material goods rather than money will increase the number of completed tasks. We perform a twenty-day, between-subjects field experiment (N=300) on a mobile crowdsourcing application and measure how often workers responded to a task notification to fill out a short survey under each incentive condition. Task completion rates increased when paying in bulk after ten tasks: doing so increased the odds of a response by 1.4x, translating into 8% more tasks through that single intervention. Payment with coupons instead of money produced a small negative effect on task completion rates. Material goods were the most robust to decreasing participation over time.