The median income of Mercer County residents was an inflation-adjusted $35,889 per year. Mercer County had 3,649 households in 2017, with a population of 8,637.
The county with the highest median resident income in the state was Williams County. Williams County's median income was $42,466 per year after adjusting for inflation – $6,577 more than Mercer County. It had 12,895 households in 2017 and a population of 32,916.
Sioux County had the lowest annual resident income among counties in North Dakota, with a median income of only $22,396 per year. That was $13,493 less than the median income in Mercer County at the time. Sioux County had 1,114 households in 2017 and a population of 4,420.
The table below shows the state's counties ranked by median annual resident earnings in 2017.