Published online by Cambridge University Press: 06 June 2003
Consider the regression
,
where
and the exact functional form of f is unknown, although we do know
that f is homogeneous of known degree r. Using a local
linear approach, we examine two ways of nonparametrically estimating
f: (i) a “direct” approach and (ii) a
“projection based” approach. We show that depending upon
the nature of the conditional variance
,
one approach may be asymptotically better than the other. Results of a small
simulation experiment are presented to support our findings.We thank Don Andrews and an anonymous referee for comments
that greatly improved this paper. The first author thanks Professor
Wolfgang Härdle for hospitality at the Institute of Statistics and
Econometrics, Humboldt University, Berlin, where part of this research
was carried out. Financial support to the first author from
Sonderforschungsbereich 373 (“Quantifikation und Simulation
Ökonomischer Prozesse”) and the NSF via grants SES-0111917 and
SES-0214081 is also gratefully acknowledged.