In the three decades since statistical procedures were first developed
to test non-nested (or separate) families of hypotheses, a burgeoning
literature has developed for testing a null model against one or more
non-nested alternatives. The purpose of the paper is to evaluate the
significance of testing empirical non-nested models, with special emph
asis on whether the theoretical literature has had a significant impac
t on practitioners, and on whether the empirical output has added sign
ificantly to our knowledge of various aspects of economics.