Data appearing as a "0" does not actually represent "0" units sold. Do to rounding issues "0" refers to less than 500 units sold.
Source: US. Bureau of the Census
Release: New Residential Sales
US. Bureau of the Census, New Houses Sold by Sales Price in the United States, Under $150,000 [NHSUSSPU15], retrieved from FRED, Federal Reserve Bank of St. Louis https://research.stlouisfed.org/fred2/series/NHSUSSPU15/, August 3, 2015.