  This Chapter is written for the Festschrift celebrating the 70th birthday of
the distinguished economist Duncan Foley from the New School for Social
Research in New York. This Chapter reviews applications of statistical physics
methods, such as the principle of entropy maximization, to the probability
distributions of money, income, and global energy consumption per capita. The
exponential probability distribution of wages, predicted by the statistical
equilibrium theory of a labor market developed by Foley in 1996, is supported
by empirical data on income distribution in the USA for the majority (about
97%) of population. In addition, the upper tail of income distribution (about
3% of population) follows a power law and expands dramatically during financial
bubbles, which results in a significant increase of the overall income
inequality. A mathematical analysis of the empirical data clearly demonstrates
the two-class structure of a society, as pointed out Karl Marx and recently
highlighted by the Occupy Movement. Empirical data for the energy consumption
per capita around the world are close to an exponential distribution, which can
be also explained by the entropy maximization principle.
