The 6th ICSA International Conference 21 - 23 July 2004, Singapore Asymptotic Mean Square Error and Convergence Rates for Stochastic Trend Estimation Prabir BURMAN Department of Statistics, University of California, Davis, USA The focus of this paper is on trend estimation for a general state-space model Yt=t+t, where the dth difference of the trend {t} is assumed to be i.i.d. and the error sequence {t} is assumed to be a mean zero stationary process. A fairly precise asymptotic expression of the mean square error is derived for the estimator obtained by penalizing the dth order differences. Optimal rate of convergence is obtained and it is shown to be ''asymptotically equivalent'' to a nonparametric estimator of a fixed trend model of smoothness of order d-.5. A criterion for selecting the penalty parameter and degree of difference d is given along with an application to the global temperature data.