Market Making and Proprietary Trading in the US Corporate Bond Market

I study broker-dealers' trading activity in the US corporate bond market. I find evidence of broker-dealer market making when customers both buy and sell a bond in a day, which happens half of the time: as predicted by market making theories with adverse selection or inventory costs, prices go down (up) as customers sell (buy). Otherwise, evidence is in favor of proprietary trading as in limits of arbitrage theories: prices go up (down) when customers sell (buy), and dealers buy (sell) bonds that are relatively cheap (expensive). Proprietary trading is reduced after the crisis. Relatedly I show that before the crisis, large broker-dealers borrowed and sold Treasury bonds in amounts similar to their corporate bond holding, but not after. I give suggestive evidence that they were subject to a severe tightening of their margin constraints as early as July 2007, in particular following increased Treasury bond volatility.