  We found a unified formula for description of the household incomes of all
society classes, for instance, of those of the European Union in year 2007.
This formula is a stationary solution of the threshold Fokker-Planck equation
(derived from the threshold nonlinear Langevin one). The formula is more
general than the well known that of Yakovenko et al. because it satisfactorily
describes not only household incomes of low- and medium-income society classes
but also the household incomes of the high-income society class.
