sentences:  In terms of ancestry, 18.4% were German, 14.6% were Irish, 13.1% were American, and 10.4% were English.Of the 18,811 households, 31.2% had children under the age of 18 living with them, 54.1% were married couples living together, 10.1% had a female householder with no husband present, 31.4% were non-families, and 27.3% of all households were made up of individuals.The average household size was 2.42 and the average family size was 2.92.