According to the survey in 2016, housing demand is far greater than the total amount of real estate available during that time. The loan crisis in 2008 is the major cause which leads to that phenomenon.
In the time of subprime crisis, property supply volume exceeds market demand, because of development of new real estate was suspended. In 2011, the American economy recovered, house purchasing became a trend again. But property development suspension leads to an imbalance between supply and demand. The trend from over supply to over demand happened after the crisis.