It is well known that the Durbin-Watson and several other tests for first-order autocorrelation have limiting power of either zero or one in a linear regression model without an intercept, and tend to a constant lying strictly between these values when an intercept term is present. This paper...

We introduce a new nonparametric approach for estimating a simple varying coeffcient model with a unit root nonstationarity. Our method is based on a piecewise local least squares principle and is computationally simple to implement. We establish its asymptotic properties and evaluate its...