Government-sponsored enterprises buy home mortgages from lenders and turn them into securities that can be bought and sold by investors, thereby encouraging home lending. Government also actively promotes exports and seeks to prevent foreign countries from maintaining trade barriers that restrict imports. Government supports individuals who cannot adequately care for themselves. Social Security, which is financed by a tax on employers and employees, accounts for the largest portion of Americans' retirement income. The Medicare program pays for many of the medical costs of the elderly. The Medicaid program finances medical care for low-income families. In many states, government maintains institutions for the mentally ill or people with severe disabilities. The federal government provides Food Stamps to help poor families obtain food, and the federal and state governments jointly provide welfare grants to support low-income parents with children. Many of these programs, including Social Security, trace their roots to the "New Deal" programs of Franklin D. Roosevelt, who served as the U.S. president from 1933 to 1945. Key to Roosevelt's reforms was a belief that poverty usually resulted from social and economic causes rather than from failed personal morals. This view repudiated a common notion whose roots lay in New England Puritanism that success was a sign of God's favor and failure a sign of God's displeasure. This was an important transformation in American social and economic thought. Even today, however, echoes of the older notions are still heard in debates around certain issues, especially welfare. Many other assistance programs for individuals and families, including Medicare and Medicaid, were begun in the 1960s during President Lyndon Johnson's (1963-1969) "War on Poverty." Although some of these programs encountered financial difficulties in the 1990s and various reforms were proposed, they continued to have strong support from both of the United States' major political parties. Critics argued, however, that providing welfare to unemployed but healthy individuals actually created dependency rather than 14