TABLE 1.

Sample Size and Years of Observation by Region in Ascending Order of Years of Follow-up

Region	Sample Size	Birth Years	Follow-up Years	Years of Follow-up
Texas	2663	1996–2003	1996–2004	9
Utah	556	1995–2003	1995–2004	10
Arkansas	362	1993–2002	1993–2003	11
Oklahoma	546	1994–2003	1994–2004	11
Colorado	972	1989–2003	1989–2004	16
North Carolina	1628	1989–1993, 1995–2003	1989–2004	16
California	4686	1983–2002	1983–2003	20
Iowa	849	1983–2003	1983–2004	22
New York	3355	1983–2003	1983–2004	22
Georgia	889	1983–2003	1983–2004	22