A common approach to comparing asset pricing models involves a competition in pricing test-asset returns. In contrast, we show that for models with traded factors, when the comparison is framed appropriately in terms of success in pricing both the test-asset and factor returns, the extent to which each model is able to price the factors in the other model is what matters for model comparison. Test assets are irrelevant based on several prominent criteria. For models with nontraded factors, test assets are relevant for model comparison insofar as they are needed to identify factor-mimicking portfolio returns.

We develop and estimate a tractable equilibrium term structure model populated with rational but heterogeneously informed traders that take on speculative positions to exploit what they perceive to be inaccurate market expectations about future bond prices. The speculative motive is an important driver of trading volume. Yield dynamics due to speculation are (1) statistically distinct from classical term structure components due to risk premiums and expectations about future short rates and are orthogonal to public information available to traders in real time and (2) quantitatively important, accounting for a substantial fraction of the variation of long maturity U. S. bond yields.

A common approach to comparing asset pricing models involves a competition in pricing test-asset returns. In contrast, we show that for models with traded factors, when the comparison is framed appropriately in terms of success in pricing both the test-asset and factor returns, the extent to which each model is able to price the factors in the other model is what matters for model comparison. Test assets are irrelevant based on several prominent criteria. For models with nontraded factors, test assets are relevant for model comparison insofar as they are needed to identify factor-mimicking portfolio returns. Received October 29, 2015; editorial decision September 6, 2016 by Editor Andrew Karolyi.

We develop and estimate a tractable equilibrium term structure model populated with rational but heterogeneously informed traders that take on speculative positions to exploit what they perceive to be inaccurate market expectations about future bond prices. The speculative motive is an important driver of trading volume. Yield dynamics due to speculation are (1) statistically distinct from classical term structure components due to risk premiums and expectations about future short rates and are orthogonal to public information available to traders in real time and (2) quantitatively important, accounting for a substantial fraction of the variation of long maturity U.S. bond yields. Received May 12, 2014; editorial decision May 10, 2016 by Editor Pietro Veronesi.