As of the census of 2010, there were 47,723 people, 17,816 households, and 11,722 families residing in the city. The population density was 1,754.6/sq mi (677.5/km²).  There were 19,806 housing units at an average density of 749.9 per square mile (289.6/km²).  The racial makeup of the city was 38.32% White (U.S. Census), 57.25% African American (U.S. Census), 1.25% Native American (U.S. Census), 1.85% Asian, 0.14% Pacific Islander (U.S. Census), 1.03% from Race (United States Census), and 1.09% from two or more races.  6.98% of the population were Hispanics in the United States or Latino (U.S. Census) of any race.
Question: How many more housing units are there than households?
Answer: 1990