Answer based on context:

There were 810,388 households out of which 28.61% had children under the age of 18 living with them, 42.80% were Marriage living together, 15.28% had a female householder with no husband present, and 36.67% were non-families. 28.79% of all households were made up of individuals and 11.07% (3.31% male and 7.76% female) had someone living alone who was 65 years of age or older. The average household size was 2.52 and the average family size was 3.14.

which household was fourth most common?
under the age of 18