Married couples with equal earnings pay higher taxes than single-earner couples

Evidence

However, once household income exceeds 1 million, almost 25 percent are eligible for the marriage bonus, compared with 45 percent who pay a marriage penalty. Why? Because almost half of those couples are equal earners—like the anonymous couple featured in Refinery29's Money Diaries in 2017, who earned 1.2 million in salaries and bonuses. The diary, written by the wife, noted that she worked full-time as an “executive director” in “finance,” and her husband worked full-time and earned a similar salary. The children were in full-day school programs, and both parents handled childcare in the evenings. — Dorothy A. Brown, The Whiteness of Wealth, 146

Categorization

• QUESTION: The 200K-1M vs >1M distinction is odd — fewer than 1M couples qualify for bonus yet the rich who are equal earners get penalized hardest. Why does the marriage penalty bite precisely at the top?