If used exactly as instructed, the estimated risk of getting pregnant is 0.3%, or about 3 in 1000 women on COCPs will become pregnant within one year. However, typical use is often not exact due to timing errors, forgotten pills, or unwanted side effects. With typical use, the estimated risk of getting pregnant is about 9%, or about 9 in 100 women on COCP will become pregnant in one year. The perfect use failure rate is based on a review of pregnancy rates in clinical trials, the typical use failure rate is based on a weighted average of estimates from the 1995 and 2002 U.S. National Surveys of Family Growth (NSFG), corrected for underreporting of abortions.