Is Nonlinear Drift Implied by the Short-End of the Term Structure?

Nonlinear drift models of the short-rate are estimated using data on the short-end of the term structure, where the cross-sectional relation is obtained by an analytical approximation. We find that (i) nonlinear physical drift is not implied unless it is strongly affected by cross-sectional dimensions of the data; (ii) nonlinear risk-neutral drift that allows for fast mean-reversion for high rates is desirable to explain and predict observed patterns of yield spreads; and (iii) for higher-frequency data from which transitory shocks are removed, (ii) still remains valid although the nonlinearity is somewhat reduced.