Using census data from over 500,000 dual-earner households in Mexico, we show that couples in which the wife earns just above half of the household income are far less common than those in which she earns just below that threshold a pattern that has been attributed to gender norms that create an aversion to wives outearning their husbands. This gap is two to five times larger than documented in the United States and Northern Europe and has grown over the 20002015 period. Unlike findings for the United States and Northern Europe, the discontinuity is not driven by equal earners, self-employed workers, or co-working couples, and persists across married and cohabiting couples, households with and without children, female-headed households, and couples where the wife is the older partner. Extending the analysis to Brazil and Panama, we find comparable patterns, establishing this as a regional rather than country-specific phenomenon. Among female same-sex couples in Mexico, we detect a similar discontinuity, whereas no consistent pattern emerges for male same-sex couples. Even when women are the primary earners, they continue to supply substantially more nonmarket labor than their male partners on average 36 more weekly hours and convergence in household production slows as the wife's income share rises further above the threshold.