1. Births: Preliminary Data for 2006. National Vital Statistics Report, Vol. 56, No. 7;Hamilton,2007
2. Births: Final Data for 2005;Martin,2007
3. Centers for Disease Control. United States All Years: Percentage of Students Who Ever Had Sexual Intercourse. 2007. Available at: http://apps.nccd.cdc.gov/yrbss/QuestYearTable.asp?path=byHT&ByVar=CI&cat=4&quest=Q57&year=Trend&loc=XX. Accessed March 2008.
4. Teenagers in the United States: Sexual Activity, Contraceptive Use, and Childbearing, 2002. Vital Health Statistics Report 23, No. 24;Abma,2004
5. An analysis of the causes of the decline in non-marital birth and pregnancy rates for teens from 1991 to 1995;Mohn;Adolesc Fam Health,2003