Empirical evidence on the expectations hypothesis of the term structure is inconclusive and its validity widely debated. Using a cointegrated VAR model of US treasury yields, this paper extends a common approach to test the theory. If, as we find, spreads between two yields are non-stationary, the expectations hypothesis fails. However, we present evidence that differences between two spreads are stationary. This suggests that the curvature of the yield curve may be a more meaningful indicator of expected future interest rates than the slope. Furthermore, we characterise level and slope by deriving the common trends inherent in the cointegrated VAR, and establish feedback patterns between them and the macroeconomy. Paper submitted to the special issue "Using Econometrics for Assessing Economic Models" edited by Katarina Juselius.