As of the census of 2000, there were 98,868 people, 38,437 households, and 27,943 families living in the county. The population density was 243 people per square mile. There were 40,554 housing units at an average density of 100 per square mile. The racial makeup of the county was 95.78% White, 1.95% Black or African American, 0.19% Native American, 0.79% Asian, 0.01% Pacific Islander, 0.28% from other races, and 1.00% from two or more races. 0.73% of the population were Hispanic or Latino of any race. There were 38,437 households out of which 33.30% had children under the age of 18 living with them, 59.50% were married couplesliving together, 9.70% had a female householder with no husband present, and 27.30% were non-families. 23.20% of all households were made up of individuals and 9.50% had someone living alone who was 65 years of age or older. The average household size was 2.54 and the average family size was 2.99. In the county, the population was spread out with 25.90% under the age of 18, 7.60% from 18 to 24, 28.40% from 25 to 44, 24.80% from 45 to 64, and 13.20% who were 65 years of age or older. The median age was 38 years. For every 100 females there were 96.20 males. For every 100 females age 18 and over, there were 92.40 males. The median income for a household in the county was $44,109, and the median income for a family was $51,169. Males had a median income of $37,357 versus $25,493 for females. The per capita income for the county was $21,669. About 5.10% of families and 6.70% of the population were below the poverty line, including 9.10% of those under age 18 and 5.60% of those age 65 or over.
2010 census
As of the 2010 United States Census, there were 102,506 people, 40,917 households, and 28,626 families living in the county. The population density was. There were 44,256 housing units at an average density of. The racial makeup of the county was 94.4% white, 2.0% black or African American, 1.2% Asian, 0.2% American Indian, 0.5% from other races, and 1.8% from two or more races. Those of Hispanic or Latino origin made up 1.3% of the population. In terms of ancestry, 34.5% were German, 13.5% were Irish, 10.2% were English, and 9.8% were American. Of the 40,917 households, 32.3% had children under the age of 18 living with them, 54.7% were married couples living together, 10.5% had a female householder with no husband present, 30.0% were non-families, and 25.3% of all households were made up of individuals. The average household size was 2.48 and the average family size was 2.95. The median age was 40.6 years. The median income for a household in the county was $51,507 and the median income for a family was $61,190. Males had a median income of $46,133 versus $32,699 for females. The per capita income for the county was $25,006. About 7.0% of families and 9.5% of the population were below the poverty line, including 14.0% of those under age 18 and 4.8% of those age 65 or over.
Politics
Miami County is a Republican stronghold county in presidential elections, with Democrats winning the county 3 times in 1912, 1936 and 1964.
