To some extent, these changing social mores have affected even behaviors that a vast majority of the country routinely judges as “morally wrong.” Since 2003, the proportion of U.S. adults saying polygamy is morally acceptable has increased by nine percentage points. Since 2001, cloning humans has seen an increase of eight points; and suicide, a six-point gain. Still, each of these items retains its essence of moral repugnancy in the nation’s social consciousness, as resounding majorities describe each of these behaviors as morally wrong.

Even among these taboo topics, married men and women engaging in an affair occupies its own space, in terms of public contempt. Over the past 15 years, no more than one in 10 U.S. adults have ever judged extramarital trysts as moral. This item has always ranked at the bottom of all issues tested in terms of moral acceptability, though at times in previous years it tied cloning humans or polygamy. In contrast to the continued, nearly universal condemnation of adultery, other topics regarding marriage and who should be having sex with whom have changed remarkably: divorce, sex between an unmarried heterosexual couple, and gay/lesbian relations have all seen double-digit increases in the percentage saying they are morally acceptable.