Income-splitting marriage bonuses favor single-wage-earner couples and penalize dual earners

Evidence

I analyzed33 2010 Census Bureau data for same-race heterosexual couples as the best proxy for the overall population, since 90 percent of the married couples responding to the census identified as same-race couples, and at the time same-sex couples were unable to file jointly. While some couples’ marriage bonuses and penalties were reduced or eliminated due to changes in qualifying income or other tax provisions like the earned income tax credit and the child tax credit, the most consistent finding was that single-wage-earner couples are more likely to receive higher benefits (and tax credits) than coequal-wage-earner couples. Single-wage-earner couples (100-0 to 90-10 split) received the greatest marriage bonus, and coequal-wage-earner couples (60-40 to 50-50 split) received the highest marriage penalty. — Dorothy A. Brown, The Whiteness of Wealth, 136

Categorization

• XREF: Connects to the reader’s existing work on structural racism as mechanism — this is the raw mechanism behind the marriage penalty claim.
• QUESTION: How did the 2017 tax reform alter or fail to alter these single-vs-dual earner splits?