The 8,878 housing units averaged 685.5 per square mile (264.7/km²), of which 6,287 (73.6%) were owner-occupied, and 2,256 (26.4%) were occupied by renters. The homeowner vacancy rate was 1.2%; the rental vacancy rate was 5.2%.  Around 17,769 people (77.1% of the population) lived in owner-occupied housing units and 5,280 people (22.9%) lived in rental housing units.. How many more housing units were owner-occupied than occupied by renters?