This paper describes the market for borrowing corporate bonds using a comprehensive data set from a major lender. The cost of borrowing corporate bonds is comparable to the cost of borrowing stock, between 10 and 20 basis points, and both have fallen over time. Factors that influence borrowing costs are loan size, percentage of inventory lent, rating, and borrower identity. There is no evidence that bond short sellers have private information. Bonds with Credit Default Swaps (CDS) contracts are more actively lent than those without. Finally, the 2007 Credit Crunch does not affect average borrowing costs or loan volume, but does increase borrowing cost variance.

Stocks are short-sale constrained when there is a strong demand to sell short and a limited supply of shares to borrow. Using data on both short interest (a proxy for demand) and institutional ownership (a proxy for supply) we find that constrained stocks underperform during the period 1988–2002 by a significant 215 basis points per month on an equally weighted basis, although by only an insignificant 39 basis points per month on a value-weighted basis. For the overwhelming majority of stocks, short interest and institutional ownership levels make short selling constraints unlikely.