  We provide an analytically treatable model that describes in a unified manner
income distribution for all income categories. The approach is based on a
master equation with growth and reset terms. The model assumptions on the
growth and reset rates are tested on an exhaustive database with incomes on
individual level spanning a nine year period in the Cluj county (Romania). In
agreement with our theoretical predictions we find that income distributions
computed for several years collapse on a master-curve when a properly
normalised income is considered. The Beta Prime distribution is appropriate to
fit the collapsed data and it is shown that distributions derived for other
countries are following similar trends with different fit parameters. The
non-universal feature of the fit parameters suggests that for a more realistic
modelling the model parameters have to be linked with specific socio-economic
regulations.
