There were 267,841 households out of which 39.4% had children under the age of 18 living with them, 35.4% were married couples living together, 25.3% had a female householder with no husband present, 5.8% had a male householder with no wife present, and 34.4% were non-families. 28.9% of all households were made up of individuals and 9.0% had someone living alone who was 65 years of age or older.  The average household size was 2.61 and the average family size was 3.24. Same-sex couple households comprised 0.8% of all households.. Which groups in average are under 4 in size?