The first television sitcom, Jackson and Jill, aired in 1949. It featured a family structure reprised in many TV shows to follow: a working husband and a stay-at-home wife . That family structure — largely fictional even back then — wasn’t just fodder for early TV comedy. It was also the premise of a monumental change to the federal tax code unveiled a year earlier. In 1948, Congress established the system of joint filing for married couples, a structure that rewards families with a sole-breadwinner.

With March being Women’s History Month, it’s a great moment to reflect on the impact of the tax code on gender justice. And there is no better place to explore that topic than in a set of groundbreaking reports published recently by the National Women’s Law Center in collaboration with several other organizations.

A powerful force shaping the economy, the tax code reflects the views and biases of those who wrote it. Over its history, the tax code has been shaped “by a small number of powerful elites, who have been largely white, male, and wealthy,” the authors explain. As such, “today’s tax code contains outdated and often biased assumptions about family structures, marriage, participation in the paid workforce, and more that work together to perpetuate structural barriers against women, families with low incomes, and people of color.”

Those structural barriers are not explicit. There is no piece of the tax code stating that women shall be treated differently than men, or people of color differently than those who are white. And yet, the biases and policy choices contained in the tax code often work to the detriment of women and people of color.

One of the biases explored in the reports is the joint tax filing system. Under this system, married couples combine their income when calculating how much in taxes they owe. Joint filers receive the benefit of tax brackets that are twice as large as the tax brackets for those who file as single. Such a system results in lower taxes for couples with one spouse serving as the main earner.

Those excluded from the “marriage bonus” include couples where both partners earn similar amounts, unmarried individuals, and couples in civil unions or domestic partnerships. In practice, this system benefits the Leave It to Beaver type families — “white, heterosexual households with a male breadwinner.” Women in same-sex married couples and Black women (who are less likely to be married and have higher labor force participation) are particularly disadvantaged under the joint filing tax system.

The joint tax filing system is only one of the many subtle disadvantages faced by women and people of color in our tax code. Others obstacles examined in the report The Faulty Foundations of the Tax Code include:

• The failure to recognize work in the home and informal caregiving as work.
• The disparate tax treatment of damages received from physical injuries at work compared to damages from workplace discrimination.
• The tax code’s large subsidies for homeownership, which disfavors groups historically excluded from housing policies — especially women of color.

This only scratches the surface. This series of reports also examines how tax policy favors the rich and corporations — to the detriment of women — and offers tools for advancing gender equity, such as well-structured refundable tax credits.

If you care about gender justice, you would do well to read this series of reports — and join the fight for a more equitable tax code.