An underlying principle of U.S. social policy is that education is the key policy lever for addressing poverty. In the United States and around the world, education is almost always heavily subsidized by government. The justifications for government involvement vary, but increasingly rely on the suggestion that expanded educational investments both strengthen the national economy and improve the societal distribution of income and welfare. Education, for example, had a prominent role in the U.S. "War on Poverty," with many of the programs developed in the 1960s continuing through today. The expansion of public colleges and universities over the past three decades has also rested on distributional arguments.