Recent decline in nonpaternity rates: a cross-temporal meta-analysis.

Nonpaternity (i.e., discrepant biological versus social fatherhood) affects many issues of interests to psychologists, including familial dynamics, interpersonal relationships, sexuality, and fertility, and therefore represents an important topic for psychological research. The advent of modern contraceptive methods, particularly the market launch of the birth-control pill in the early 1960s and its increased use ever since, should have affected rates of nonpaternity (i.e., discrepant genetic and social fatherhood). This cross-temporal meta-analysis investigated whether there has been a recent decline in nonpaternity rates in the western industrialized nations. The eligible database comprised 32 published samples unbiased towards nonpaternity for which nonoverlapping data from more than 24,000 subjects from nine (mostly Anglo-Saxon heritage) countries with primarily Caucasian populations are reported. Publication years ranged from 1932 to 1999, and estimated years of the reported nonpaternity events (i.e., the temporal occurrence of nonpaternity) ranged from 1895 to 1993. In support of the hypothesis, weighted meta-regression models showed a significant decrease (r = -.41) of log-transformed nonpaternity rates with publication years and also a decrease, albeit not significant (r = -.17), with estimated years of nonpaternity events. These results transform into an estimated absolute decline in untransformed nonpaternity rates of 0.83% and 0.91% per decade, respectively. Across studies, the mean (and median) nonpaternity rate was 3.1% (2.1%). This estimate is consistent with estimates of 2 to 3% from recent reviews on the topic that were based on fewer primary studies. This estimate also rebuts the beliefs and hearsay data widespread among both the public and researchers which contend nonpaternity rates in modern populations might be as high as about 10%.