Peer Effects among Swimmers

We develop a novel identification strategy and examine various aspects of peer effects using swimming data. We find that the performance of adjacent competitors positively influences swimmers' performances. In particular, swimmers are influenced by slower-lane peers, suggesting that being chased improves one's performance. We use absenteeism data to directly compare the performances of swimmers with and without peers. We have found that swimmers swim faster with peers swimming behind them than when swimming alone, but that they swim slower with peers swimming ahead. Finally, we find that observability is a key determinant of peer effects, by comparing freestyle and backstroke competitions.