The study looked at how changes in who was buying homes and how much credit they were getting may have affected the housing market before the 2008 financial crisis. They found that the relationship between mortgage size and income during the housing boom was similar to before, but buyers in areas with big price increases had higher incomes. Poorer areas saw more mortgages being given out, but they were in line with borrower incomes. Most mortgage debt was held by middle and high-income borrowers, who also had the most defaults after 2007. This suggests that people were buying into a housing bubble based on high prices, rather than changes in how loans were given out.