Editing Natural experiment (section)

===Vietnam War draft===

An important question in economics research is what determines earnings. Angrist (1990) evaluated the effects of military service on lifetime earnings.<ref name = "Angrist">{{cite journal |last=Angrist |first=Joshua D. |year=1990 |title=Lifetime Earnings and the Vietnam Draft Lottery: Evidence from Social Security Administrative Records |journal=[[American Economic Review]] |volume=80 |issue=3 |pages=313–336 |jstor=2006669 }}</ref> Using statistical methods developed in [[econometrics]],<ref>{{Cite web|url=https://www.youtube.com/watch?v=OUN6Gp_H3q4|title=Natural experiments in econometrics|date=4 August 2013 |via=www.youtube.com}}</ref> Angrist capitalized on the approximate [[random assignment]] of the [[draft lottery (1969)|Vietnam War draft lottery]], and used it as an [[instrumental variable]] associated with eligibility (or non-eligibility) for military service. Because many factors might predict whether someone serves in the military, the draft lottery frames a natural experiment whereby those drafted into the military can be compared against those not drafted because the two groups should not differ substantially prior to military service. Angrist found that the earnings of veterans were, on average, about 15 percent less than the earnings of non-veterans.<ref name = "Angrist"/>