You will also see divorce rates in the 20-30% range. I think these are census bureau data which counts all people over 15 yrs. old who have ever been divorced. The 50% number counts only people who have been married and multiple counts people who have been divorced several times.

See: Change in the Reporting of Marriage and Divorce Statistics at the National Center for Health Statistics (NCHS) at www.cdc.gov/nchs

Source: Table 83 on p. 4 of pdf of Section 2 of 2003 Statistical Abstract of the U.S., at www.census.gov/prod/2004pubs/03statab/vitstat.pdf

Source: U. Maryland

Stats

• 2000 Census 11.9% of Americans 15 and up are divorced or separated.
• The ratio of marriages to divorces is 2 to 1.
• 43 Percent of First Marriages Break Up Within 15 Years. (CDC Study 2001)
• 95 percent of all divorced people eventually remarry. (Google answers)
• Divorce rate/year in 1996 was 4.3 per 1,000 people.
• 60 sixty percent of second marriages fail. (Families Northwest)
• 56 percent of people over 15 are married and living with their spouses in 1998.
  10 percent Currently Divorced
  Others Never married, separated, widowed
  See US Population Page
• Census Bureau data:
  Marital History for People 15 Years Old and Over (2001) at census.gov

  Status Percent	Men	Women
  Never married	29.0	21.8
  Ever married	71.0	78.2
  Married once	54.4	60.2
  Married twice	13.1	14.6
  Married 3 or more times	3.5	3.4
  Still Married	58	55
  Ever divorced	21.9	24.2
  Currently divorced	8.9	10.8
  Ever widowed	3.6	12.1
  Currently widowed	2.4	10.6

Ever Divorced Rates for:

                  All- men: 21.9%, women: 24.2%
 White (non-Hispanic)- men: 23.3%, women: 25.4%
                Black- men: 18.8%, women: 20.1%
             Hispanic- men: 12.7%, women: 15.9%
                Asian- men:  8.8%, women: 10.4%

Links:
Justin Wolfers reports at Wharton
U. Maryland data
Rates by Religion
Marriage Statistaics at biblenews1.com
Fact Sheet on Divorce in America