Higher education in the United States is an optional stage of formal learning following secondary education. Higher education, also referred to as post-secondary education, third-stage, third-level, or tertiary education occurs most commonly at one of the 4,360 Title IV degree-granting institutions, either colleges or universities in the country. These may be public universities, private universities, liberal arts colleges, community colleges, or for-profit colleges. America higher education is loosely regulated by several third-party organizations. Long-running social problems in terms of the history of the U.S. such as discrimination and poverty have significantly impacted trends in American learning over multiple decades. Within this vast estate many issues arise for government, staff and students. Medical education in the college and university context as a specific topic has received specialized analysis for decades given the importance of health in America. Educational pipeline US college students come from three major sources: the US K-12 pipeline, adult or non-traditional students, and foreign students. Projections about future enrollment patterns are based on demographic projections about these groups. K–12 education As of 2017, the US ranks fifth from the bottom among OECD nations, in terms of poverty gap and fourth from the bottom in terms of poverty rate. Jonathan Kozol has described these inequalities in K-12 education in Savage Inequalities and The Shame of the Nation: The Restoration of Apartheid Schooling in America. In a 1998 Brookings Institution paper "Unequal Opportunity: Race and Education," Linda Darling-Hammond stated that "educational outcomes for minority children are much more a function of their unequal access to key educational resources, including skilled teachers and quality curriculum, than they are a function of race." In 2016, the American Psychological Society added that racial bias by teachers and administrators is also a factor in student outcomes. This affects how teachers teach and administrator's discipline students. More than half of U.S. students go to "racially concentrated" schools. Twenty percent of US students are enrolled in districts that are poor and nonwhite, but only 5 percent live in poor white districts. To make matters worse, the number of school districts in the United States has been increasing, reflecting a growing race and social class divide. About a half a million high schools students are not prepared for college when they enroll and require remedial education. Adult or nontraditional students Adult or nontraditional students are those that do not matriculate immediately after high school graduation. This includes