  We derive an empirical formula for the width of quantum Hall effect plateaus
which is free of adjustable parameters. It describes the integer, fractional
and $\nu = 0$ (Wigner insulator) quantum Hall effect in single heterojunctions.
The temperature scale of the existence of these three phenomena is the same as
the melting temperature of a classical Wigner crystal. We conclude that the
basic assumption of the current theory of QHE that the plateau width is
determined by the disorder is highly improbable.
