We study peer effects in the workplace. Specifically, we investigate whether, how, and why the productivity of a worker depends on the productivity of coworkers in the same team. Using high-frequency data on worker productivity from a large supermarket chain, we find strong evidence of positive productivity spillovers from the introduction of highly productive personnel into a shift. Worker effort is positively related to the productivity of workers who see him, but not workers who do not see him. Additionally, workers respond more to the presence of coworkers with whom they frequently interact. We conclude that social pressure can partially internalize free-riding externalities that are built into many workplaces. (JEL J24, L81, M54)

We survey the evidence on whether racial attitudes negatively affected Barack Obama’s vote share in the 2008 presidential election. There is some evidence pointing toward this possibility. First, the increase in the Democratic vote share in the presidential election between 2004 and 2008 was relatively smaller in Appalachia and some Southern states. Second, there was a significantly smaller 2004–2008 growth in votes for the Democratic presidential candidate than Democratic House of Representatives candidates. While these patterns are consistent with the possibility that racial attitudes lowered the number of votes for Obama, a more complete examination of available data casts doubt on this interpretation. We examine whether Barack Obama underperformed in parts of the country where voters are more racially biased, on average. Specifically, we test whether the loss of votes experienced by Obama (compared to John Kerry) relative to the votes that one may have predicted based on the general increase in the number of Democratic votes in House elections between 2004 and 2008 was larger in states where the white population is more racially biased, on average. We measure racial attitudes using data from the General Social Survey on the fraction of white voters who support anti-interracial-marriage laws. We find little evidence that Obama underperformed relative to congressional Democrats in states that have a white electorate with stronger racial bias. We also find little evidence that turnout was higher among segments of the