Maximum wage, also referred to as wage ceiling, and often tied to a wage ratio is an approach often used to justify slowing increases in inequality. President Franklin Roosevelt suggested a maximum wage of $25,000 during WWII, which led to the imposition of a marginal tax rate of 93% on upper incomes. Wikipedia offers a good overview. Robely George, in his book Socioeconomic Democracy, offers an approach that would limit Maximum Allowable Wealth (MAW) by tying it directly, through a democratic process, to a Universally Guaranteed Personal Income (UGI).