In 2000 there were 79,667 households out of which 38.70% had children under the age of 18 living with them, 61.90% were married couples living together, 10.20% had a female householder with no husband present, and 24.20% were non-families. 19.70% of all households were made up of individuals and 6.80% had someone living alone who was 65 years of age or older.  The average household size was 2.72 and the average family size was 3.14.. which household was least common?