Using Census Bureau data, that gap translates to a difference of more than 14 million homes, Zillow said Tuesday. The results are in line with Zillow’s expectation that 25% more homes will sell in 2021 than in 2020, feeding a surge in demand triggered by the pandemic and ultra-low mortgage rates.  “That injection of inventory could give buyers more options and breathing room in a competitive market,” Chris Glynn, principal economist at Zillow, said in a statement. “The vaccine, however, will also likely add to already-strong demand, given that most sellers will become buyers as they trade in for a home that better suits their new needs.”  For those that are already willing to sell, surging prices have been a big factor. The S&P CoreLogic Case-Shiller U.S. National Home Price NSA Index rose 10.4% in 2020, the biggest annual gain since 2013, according to figures released Tuesday.