The median income of Madison County residents was an inflation-adjusted $31,296 per year. Madison County had 6,357 households in 2017, with a population of 15,720.
The county with the highest median resident income in the state was Dallas County. Dallas County's median income was $42,700 per year after adjusting for inflation – $11,404 more than Madison County. It had 31,363 households in 2017 and a population of 80,864.
Decatur County had the lowest annual resident income among counties in Iowa, with a median income of only $19,872 per year. That was $11,424 less than the median income in Madison County at the time. Decatur County had 3,172 households in 2017 and a population of 8,105.
The table below shows the state's counties ranked by median annual resident earnings in 2017.