Members of Congress are less likely to vote for pro-draft measures if they have family members who could be shipped off to war, according to a new analysis published by the National Bureau of Economic Research Monday.

The study, which reviewed the votes of thousands of legislators during World War I, World War II, the Korean War and the Vietnam War, provides a glaring example of a dynamic that is often obscured in politics: Politicians vote differently when they or their own families are likely to be affected by the bill in question.

"[R]epresentative democracy may better enhance social welfare when voters are aware of legislators' private incentives," conclude the authors, including economists associated with Brown and Yale Universities.

The paper, which has not yet undergone peer review, reviewed 249 roll call votes in the Senate and House of Representatives between 1917 and 1974, cross-checked with data about legislators' families.

The economists found that lawmakers with draft-eligible sons were 10 percent to 17 percent less likely to vote for conscription than politicians with daughters of the same age. In other words, in an apples-to-apples comparison, senators and representatives whose own families might have been affected by the draft were less likely to support it.

Lawmakers whose sons aged out of draft eligibility subsequently became significantly more supportive of the draft, suggesting that they are mostly looking out for themselves when they go to vote. Still, those votes made them better aligned with voters, who generally are less likely to favor the draft if it seems like there's a war coming.