Figure . Millennium Cohort Study Flow of Participants From Original Sample to Baseline and Follow-up Enrollments to Final Study Population.
aThe 2560 individuals included in the pilot or feasibility study were removed from the mailing list so they would not receive an additional survey.
bIndividuals were considered ineligible if they had an invalid Social Security number, were not serving in the military as of October 1, 2000, or if the survey was filled out by someone other than the invited individual.