The role of geographic scale in testing the income inequality hypothesis as an explanation of health disparities

► Demonstrates that a measure of income inequality varies systematically across geographic scale in terms of magnitude and precision. ► Shows income inequalities measured at different geographic scales have different interpretations. ► Concludes that a rejection of income inequality hypothesis (IIH) at one level does not negate positive evidence at another level. ► Stresses assessment across a variety of scales is needed to have a comprehensive picture of the IIH in any given study. ► Suggests different mechanisms of IIH exist for different sex groups and health indicators, in addition to geographic scale.