PT - JOURNAL ARTICLE AU - Solon, Gary AU - Haider, Steven J. AU - Wooldridge, Jeffrey M. TI - What Are We Weighting For? AID - 10.3368/jhr.50.2.301 DP - 2015 Mar 31 TA - Journal of Human Resources PG - 301--316 VI - 50 IP - 2 4099 - http://jhr.uwpress.org/content/50/2/301.short 4100 - http://jhr.uwpress.org/content/50/2/301.full SO - J Hum Resour2015 Mar 31; 50 AB - When estimating population descriptive statistics, weighting is called for if needed to make the analysis sample representative of the target population. With regard to research directed instead at estimating causal effects, we discuss three distinct weighting motives: (1) to achieve precise estimates by correcting for heteroskedasticity; (2) to achieve consistent estimates by correcting for endogenous sampling; and (3) to identify average partial effects in the presence of unmodeled heterogeneity of effects. In each case, we find that the motive sometimes does not apply in situations where practitioners often assume it does.