The average population density was 11,457 people per square mile (4,405.4/km²). The Census reported that 1,468,623 people (96.2% of the population) lived in households, 38,007 (2.5%) lived in non-institutionalized group quarters, and 19,376 (1.3%) were institutionalized. In 2013, the city reported having 668,247 total housing units, down slightly from 670,171 housing units in 2010. As of 2013[update], 87 percent of housing units were occupied, while 13 percent were vacant, a slight change from 2010 where 89.5 percent of units were occupied, or 599,736 and 10.5 percent were vacant, or 70,435. Of the city's residents, 32 percent reported having no vehicles available while 23 percent had two or more vehicles available, as of 2013[update].
What percent are vacant as of 2013? (If the question is unanswerable, say "unanswerable")
13 percent