Taking advantage of the different trading behaviors of investors on same-issuer bonds, we show that informed trading lies at the core of the momentum effect for corporate bonds. We split the firm-level bond cross-section into top (nontop) bonds that are characterized by higher (lower) volumes of institution-sized trades. We show that top bonds attract more informed trading and transmit information faster than nontop bonds. We design specific top and nontop bond momentum strategies to capitalize on this informational heterogeneity. The results indicate that fast news spreading yields short-lived momentum in top bonds, whereas momentum in nontop bonds is strong and drawn-out due to slow information diffusion. These differences are concentrated in bond-level information-intensive periods and are not explained by differences in liquidity levels, systematic risk (including liquidity risk), bond characteristics, and market states. In particular, bond-level liquidity affects the momentum effect only by altering the rate at which news spreads.

We show that momentum profits for corporate bonds depend on the state of the market (UP/DOWN), as already documented for equities. Momentum gains exclusively follow UP periods. In contrast, DOWN markets herald momentum losses. Importantly, this study links momentum gains to underpricing, as measured by low sentiment. In particular, the UP-market momentum gains are generated exclusively by momentum portfolios formed in periods of low sentiment. The DOWN-market reversal returns in low sentiment are even larger than the UP-market momentum gains. We also introduce a novel top-volume bond momentum strategy and show that it yields large and persistent unconditional profits.