Economists increasingly accept that social norms have powerful effects on human behavior and outcomes. In recent history, one norm widely adhered to in most developed nations has been for men to be the primary breadwinner within mixed-gender households. As women have entered the labor market in greater numbers and gender wage differentials have declined, female breadwinning has become more common in such nations. Has this been accompanied by worse outcomes in non-monetary realms, due to the violation of the male breadwinning norm? This would be evidence that norms act to slow the pace of social evolution. We use household data from two countries to examine whether female breadwinning makes partnerships less healthy or less stable. US data from the late twentieth century shows that female breadwinning is associated with significantly more partnership problems for older couples in cross-sections and for younger couples in fixed-effects specifications. Examining more recent US and Australian data, we find that female breadwinning is associated with a modestly higher dissolution risk and a fall in some measures of reported relationship quality, but mainly for young people in cohabiting partnerships and men in less educated partnerships. We interpret these results to reflect changing social norms, plus relationship market dynamics arising from differences in the ease of access to superior partnership alternatives for women who out-earn their partners. While gender-specific breadwinning norms may be fading with time, economic realities and marriage market dynamics continue to be drivers of behavior and outcomes.