The higher one's income, the greater the fraction of it that tends to consist of economic rent rather than rewards for any commensurate contribution to production. By definition, economic rent is a factor payment exceeding that required to place a factor in its most productive use, so it can be taxed away entirely without impairing wealth production. Consequently, in the absence of taxes specifically levied on economic rent, a steeply progressive tax on the highest incomes can be expected to fall almost exclusively on economic rent, minimizing the excess burden of such taxation.
In a market economy, the larger an investment is, the higher its rate of return. This is due to both economies of scale and the increased range of investment opportunities. In addition to these economic forces, those who control greater amounts of capital within a society are able to participate more directly in shaping government policy, often in ways that further maximize their wealth. Thus, due to both economic and political realities within a market economy, it is a natural process for the wealthiest individuals and firms in a society to become disproportionately wealthier over time. In order to prevent the political instability resulting from the natural stratification of the populace into an ever smaller and wealthier aristocracy or moneyed class, and an ever larger working class, all free market democracies engage in progressive taxation and programs to enhance economic opportunity for the lower and middle classes.[citation needed]
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