Absence of Age-Income Correlation in Ten Rural South Dakota Counties: Real Capital Outflow or Self-selection Bias?

Previous research establishes a positive correlation between age and income during the working years of 18 to 65. Survey data from the first 10 communities in a development project in South Dakota do not exhibit this correlation. Census data is examined for the 10 counties involved to determine whether the correlation is absent countywide or if self-selection bias may have produced this result. With income distributions matching their respective counties and working age distributions that do not, factors that might skew self-selection in the observed manner are examined from a life-course perspective.