As of the census of 2000, there were 156,951 people, 55,384 households, and 43,531 families residing in the county. The population density was 276 people per square mile (107/km²). There were 58,919 housing units at an average density of 104 per square mile (40/km²). The racial makeup of the county was 97.13% White, 0.46% Black or African American, 0.43% Native American, 0.57% Asian, 0.03% Pacific Islander, 0.32% from other races, and 1.06% from two or more races. 1.24% of the population were Hispanic or Latino of any race. 21.0% were of German, 11.5% Irish, 11.2% English, 10.4% Polish, 7.9% American and 6.0% Italian ancestry according to Census 2000. 96.8% spoke English and 1.1% Spanish as their first language.
There were 55,384 households out of which 39.80% had children under the age of 18 living with them, 68.50% were married couples living together, 6.80% had a female householder with no husband present, and 21.40% were non-families. 17.10% of all households were made up of individuals and 5.40% had someone living alone who was 65 years of age or older. The average household size was 2.80 and the average family size was 3.18.
In the county the population was spread out with 28.80% under the age of 18, 6.60% from 18 to 24, 31.70% from 25 to 44, 24.60% from 45 to 64, and 8.30% who were 65 years of age or older. The median age was 36 years. For every 100 females there were 102.10 males. For every 100 females age 18 and over, there were 99.70 males.
With a median household income of $67,400, and a median family income of $75,284, Livingston county is one of the Highest-income counties in the United States. Males had a median income of $54,358 versus $32,073 for females. The per capita income for the county was $28,069. About 2.40% of families and 3.40% of the population were below the poverty line, including 3.60% of those under age 18 and 4.50% of those age 65 or over.
Livingston County has been the fastest growing county in the state for the past decade and also through the 1970s. More than 50% of all the population of Livingston County is located in the southeastern communities of Brighton Township, Genoa Township, Hamburg Township, Green Oak Township, the Village of Pinckney, Putnam Township and the City of Brighton.
The US Census Bureau in 2000 identified Brighton, Howell, and the nearby city of South Lyon to be a contiguous, urbanized area, one of the newest such areas in the United States.
By 2006 the county population had grown 17.6% to 184,511. Livingston County is the fastest-growing county in Michigan.
In 2006, non-Hispanic whites made up 95.7% of the county population; African-Americans made up 0.7%; Asians 0.8%; and Native Americans 0.4%. Hispanics were 1.6% of the population.