From Zillow: Q1 2016 Negative Equity Report: Rust Belt Overtakes Sand States as Nation’s Nest of Negative Equity

The national negative equity rate – the share of all homeowners with a mortgage who are underwater, owing more on their mortgage than their home is worth – fell to 12.7 percent in the first quarter of 2016, according to the first quarter Zillow Negative Equity Report. The U.S. negative equity rate is down from 13.1 percent in Q4 2015 and 15.4 percent a year ago, and has fallen or stayed flat from the prior quarter for 16 straight quarters after peaking at 31.4 percent in Q1 2012 (figure 1).
emphasis added

The following graph from Zillow shows a time series for negative equit.

Zillow Negative EquityClick on graph for larger image.

From Zillow:

The steady decline in negative equity nationwide has been driven by a consistent recovery in home values over the past several years. But while home values have risen to some extent in a large majority of U.S. markets, some markets have recovered much more quickly than others, and the concentration of negative equity nationwide has shifted from the Southwest and Southeast to the Midwest