Napier and Jost (2008) noted that conservatives are generally happier than liberals, and that this is mediated by differences in rationalization of inequality. Using national data collected between 1974 and 2004, they assessed increases in income inequality during that time period. They then looked at the difference in happiness between liberals and conservatives as a function of increasing inequality over time. How should they analyze these data? (Liberals always reported less happiness than conservatives, and their decrease in happiness as a function of changes in income equality was far steeper than similar decreases for conservatives.)