The EKC is an essentially empirical phenomenon, but most of the EKC
literature is econometrically weak. It is very easy to do bad econometrics and the
history of the EKC exemplifies what can go wrong. The EKC idea rose to
prominence because few paid sufficient attention to econometric diagnostic
statistics. Little or no attention has been paid to the statistical properties of the
data used such as serial dependence or stochastic trends in time series and few
tests of model adequacy have been carried out or presented. However, one of
the main purposes of doing econometrics is to test which apparent relationships,
or "stylized facts", are valid and which are spurious correlations
hypothesized income inequality first rises and then falls as economic
development proceeds
development proceeds.