Barber County's population was estimated to be 4,974 in the year 2006, a decrease of 318, or -6.0%, over the previous six years.
As of the U.S. Census in 2000, there were 5,307 people, 2,235 households, and 1,510 families residing in the county. The population density was 5 people per square mile (2/km²). There were 2,740 housing units at an average density of 2 per square mile (1/km²). The racial makeup of the county was 97.06% White, 0.38% Black or African American, 0.58% Native American, 0.09% Asian, 0.89% from other races, and 1.00% from two or more races. Hispanic or Latino of any race were 2.02% of the population.
There were 2,235 households out of which 28.70% had children under the age of 18 living with them, 58.70% were married couples living together, 6.50% had a female householder with no husband present, and 32.40% were non-families. 29.90% of all households were made up of individuals and 17.00% had someone living alone who was 65 years of age or older. The average household size was 2.35 and the average family size was 2.91.
In the county the population was spread out with 25.00% under the age of 18, 5.80% from 18 to 24, 23.20% from 25 to 44, 24.50% from 45 to 64, and 21.50% who were 65 years of age or older. The median age was 43 years. For every 100 females there were 92.40 males. For every 100 females age 18 and over, there were 89.40 males.
The median income for a household in the county was $33,407, and the median income for a family was $40,234. Males had a median income of $29,806 versus $20,046 for females. The per capita income for the county was $16,627. About 7.50% of families and 10.10% of the population were below the poverty line, including 12.60% of those under age 18 and 4.90% of those age 65 or over.