Some of the cities that have the most units under construction right now—such as Los Angeles, for example,—do not have a big chunk in the planning stages.
Fannie Mae and Freddie Mac held 37 percent ($467 billion) of all mortgages on multifamily properties outstanding as of Sept. 30, 2017, according the Federal Reserve data.
The cost of materials important to the construction of apartments rose 3.6 percent over the year that ended in September, according to the producer price index from the Bureau of Labor Statistics.