19
https://www.urban.org/research/publication/housing-affordability-gap-extremely-low-income-r
20
http://www.pewsocialtrends.org/2014/02/11/the-rising-cost-of-not-going-to-college/
21
https://www.econ.umd.edu/publicationprofile/1860
22
http://economics.mit.edu/files/12736
23
https://web.williams.edu/Economics/wp/BakijaColeHeimJobsIncomeGrowthTopEarners.pdf
24
http://www.washingtonpost.com/sf/business/2014/12/19/fixing-the-broken-talent-flow/
25