In this paper Kuznets' U-curve hypothesis is tested on two unbalanced panel
data sets of 47 and 62 countries, for the period 1970-93, using two-way fi
xed and random effects models. Several competing model specifications are e
stimated and the one best fitting the data is selected by appropriate model
selection procedures. It is shown that there is no hard empirical evidence
to support the usual econometric model formulations and the U-curve hypoth
esis.