Holding most of the control variables constant at 1990 levels fails to account for the geographic mobility of Americans.

Next, the researchers tested 48 "control variables." The purpose of these adjustments is to account for factors unrelated to USAID spending that affect mortality rates.

Holding control variables constant at 1990 levels ignores important changes that occurred on a yearly basis between 1994 to 1999.

Notably, keeping all other control variables constant in the logistic model, women from female-headed households were 31 percent less likely to experience the death of a child (odds ratio = 0.69 ...