Since about 1970, California has been experiencing an extended and increasing housing shortage, such that by 2018, California ranked 49th among the states of the U.S. in terms of housing units per resident. This shortage has been estimated to be 3-4 million housing units (20-30% of California's housing stock, 14 million) as of 2017. Experts say that California needs to double its current rate of housing production (85,000 units per year) to keep up with expected population growth and prevent prices from further increasing, and needs to quadruple the current rate of housing production over the next seven years in order for prices and rents to decline.