Western, Bruce and Deirdre Bloome, 2009, "Variance Function Regressions for Studying Inequality," Sociological Methodology, 39: 293-326.
Although theory usually focuses on between-group differences, within-group variance also contributes to inequality. Within-group inequality can be measured by the residual variance of a regression. Typically the residual is viewed as unexplained, and its variation is not treated as substantively interesting. Although it is often overlooked, residual heterogeneity may vary in substantively important ways. Some groups may be more insecure than others, or vary more in unobserved characteristics. The structure of within-group inequality may be especially important for sociological analysis where the residual variance often greatly exceeds the between-group variance.
residual variance(within-group variance)をモデル化するという話。residual varianceへの注目は、アメリカの労働経済学ではしばしば見られる(SBTCの議論)。