Since October 2008, fixed rates for interest rate swaps with a 30-year maturity have been mostly below Treasury rates with the same maturity. Under standard assumptions, this implies the existence of arbitrage opportunities. This paper presents a model for pricing interest rate swaps, where frictions for holding bonds limit arbitrage. I analytically show that negative swap spreads should not be surprising. In the calibrated model, swap spreads can reasonably match empirical counterparts without the need for large demand imbalances in the swap market. Empirical evidence is consistent with the relation between term spreads and swap spreads in the model. Received April 16, 2017; editorial decision Januray 3, 2019 by Editor Stijn Van Nieuwerburgh

We examine the causal effect of limits to arbitrage on 11 well‐known asset pricing anomalies using the pilot program of Regulation SHO, which relaxed short‐sale constraints for a quasi‐random set of pilot stocks, as a natural experiment. We find that the anomalies became weaker on portfolios constructed with pilot stocks during the pilot period. The pilot program reduced the combined anomaly long–short portfolio returns by 72 basis points per month, a difference that survives risk adjustment with standard factor models. The effect comes only from the short legs of the anomaly portfolios