U.S. homes are selling 30 days faster now than they were a year ago, according to a new report from Zillow.
This September, home listings spent an average of 86 days on Zillow.
Tight inventory was the main reason for this, according to Zillow chief economist Stan Humphries:
"The inventory constraints we’re seeing are a big factor, which are caused by the imbalance of supply and demand between buyers wanting to enter the market to take advantage of low mortgage rates, and would-be sellers that are stuck underwater and unable to list their homes. Almost every market we track is seeing less inventory this year relative to last year.
"New construction is also ramping up more slowly than demand because builders have largely consumed their ready-to-build parcels and are having to entitle new land which can be a lengthy process, particularly with fewer municipal staff in permitting and related offices than during the boom years."
The best performing metros were Sacramento, Las Vegas, and San Antonio, where the number of days spent as a listing declined by 43, 44, and 37 days respectively.
"Relative to peak levels, home values are still down more than 30% in Sacramento and down almost 50% from peak in Las Vegas," Humphries told Business Insider in an email. "Investor demand in Sacramento and Las Vegas has also driven up both prices and demand in these areas, helping homes to sell much faster than in markets where investors may be less attracted."
San Antonio, on the other hand, is benefiting from a jump in employment and people moving in for jobs. The region's employment rate, at 6.4%, has been much lower than the national average. 
The survey looked at the 30 largest metro areas covered by Zillow.