Marriage across racial and ethnic lines has reached a new high in the U.S. amid fading social taboos in an ever more diverse society.

About 15% of new marriages in the U.S. in 2010 were between individuals of a different race or ethnicity, more than double the share in 1980, according to a report released Thursday by the Pew Research Center. Among those married in 2010, 9% of whites, 17% of blacks, 26% of Hispanics and 28% of Asians married outside their ethnic or racial group.

"Intermarriage...