rates once at a university. According to a 2008 study, students with a low socioeconomic status study less, work more hours, have less interaction with faculty, and are less likely to join extra-curricular activities. 42% of students with low socioeconomic status indicated that they worked more than 16 hours a week during school, with a high percentage working up to 40 hours a week, although such students may benefit since potential employers assign great importance to a graduate's work experience. This is also evidence of a positive relation between socioeconomic status and social integration at university. In other words, middle-class students take part in more formal and informal social activities and have a greater sense of belonging to their universities than do working-class students. Completion Suzanne Mettler notes in her book, Degrees of Inequality, that in 1970 40% of US students in top income quartile had achieved a bachelor's degree by the age of 24. By 2013, this percentage rose to 77%. For students in the bottom income quartile, only 6% had earned a bachelor's degree in 1970. By 2013, this percentage was still at a marginal 9%. Unfortunately, there have been and continue to be many barriers for students of lower socioeconomic status to get access. There are certain organizations and programs that have capitalized on the idea that attaining a college degree, specifically at a top tier university, is critical to social mobility. Organizations like QuestBridge, a non-profit focused on helping students of low socioeconomic status and minority background, have helped historically underrepresented groups attain a significant degree of social advantage. QuestBridge is partnered with the nation's top 38 colleges and has helped over 13,000 students gain entrance into these universities since 2004. However, even these accomplishments are minuscule, when we recognize that there are between 25,000 and 35,000 low income students that are qualified to gain entrance into the nation's top universities each year, but do not even apply. By these standards, QuestBridge has served less than 4% of the students that they focus on. Race and ethnicity From the 1950s to the 2010s, the United States higher education system was increasingly viewed as a vehicle for social mobility and economic equality. As a result, there was a clear struggle to try and open access to higher education for the wider population so that more individuals could benefit from this economic good. Programs like affirmative action were