This is the median number of months for sale since the completion of the home.
Source: US. Bureau of the Census
Release: New Residential Sales
US. Bureau of the Census, Median Number of Months on Sales Market for Newly Completed Homes [MNMFS], retrieved from FRED, Federal Reserve Bank of St. Louis https://research.stlouisfed.org/fred2/series/MNMFS/, September 2, 2015.