The importance of homogeneity as a restriction on functional forms has been well recognized in economic theory. Imposing additive separability is also quite popular since many economics models become easier to interpret and estimate when the explanatory variables are additively separable. In...

Consider the regression y = f(x) + e ' where E (e | x) = 0 and the exact functional form of f is unknown, although we do know that it is homogeneous of known degree r. Using a local linear approach we examine two ways of nonparametrically estimating f: (i) a "direct" or "numeraire" approach, and...

Consider the regression y = f(x) + e ' where E (e

The importance of homogeneity as a restriction on functional forms has been well recognized in economic theory. Imposing additive separability is also quite popular since many economics models become easier to interpret and estimate when the explanatory variables are additively separable. In...

This paper develops a new econometric tool for evolutionary autoregressive models where the AR coefficients change smoothly over time. To estimate the unknown functional form of time-varying coefficients, we propose a mdified local linear smoother. The asymptotic normality and variance of the...