Americans like to celebrate their Constitution, their country’s foundational document, which enshrines certain inalienable rights. But it turns out these days the US Constitution is less distinctive for what equal rights it does uphold, and more for which ones it fails to.

In a study published today by UCLA, researchers compared the constitutions of 193 UN member states to assess which protect equal rights for its citizens irrespective of their differences, including gender, sexual orientation, income, and disability.

“There is no opportunity for equality if people don’t have equal legal rights,” Jody Heymann, a UCLA School of Public Health professor who led the research, told Quartz. The fact that a right might be provided in a country’s constitution doesn’t guarantee that it is granted to its citizens, of course, yet it does create an important legal precedent.

The comparison between global constitutions revealed encouraging progress in the past two decades. All of the constitutions passed since 2000 include provisions for gender rights, as well as a right to health care.

On the other hand, many older constitutions fall short. As a result, there is a disparity of constitutional guarantees for the citizens of countries with more recent constitutions and those who live in countries with older constitutional histories.

The United States stands out in this disparity: Compared to its global peers, the United States fails to guarantee all kinds of rights.

The US constitution is one of just 28 worldwide, for example, that doesn’t guarantee gender equality. While Congress passed the Equal Rights Amendment in 1972, guaranteeing gender equality, some states have been slow to approve it, delaying its adoption as a new amendment to the Constitution. The US Constitution also doesn’t protect the right to health care, unlike 142 other global constitutions. Some 160 constitutions worldwide guarantee a right to education, but the United States does not. Similarly, equal rights for people with disabilities and members of the LGBTQ community are not protected by the US Constitution. Landmark court decisions have outlawed discrimination of those groups, but they are still at risk of possible reversal and debate, as seen in the recent Supreme Court case debating whether sexual orientation can be grounds for firing.

Aleta Sprague, a legal analyst at the WORLD Policy Analysis Center, a nonprofit, said that constitutional rights are engrained in the fabric of a nation, and are often quoted in the context of policy and lawmaking debate. A constitution also endures longer than other pieces of legislation. So while some groups might be protected by various laws, they are rarely as powerful as a constitutional guarantee.

Even in the cases where rights aren’t immediately translated into legislation, Heymann says, their presence in the constitution tends to lead to positive results in the achievement of such rights. As an example, she mentions the right to health in the United States. Although it is not guaranteed in the US Constitution, it is included in some state constitutions. These states, Heymann says, have reduced infant mortality by a staggering 8%.

“The constitution is a powerful tool to change norms and introduce change,” Amy Raub, a policy analyst at WORLD, told Quartz. She cites South Africa. The South African constitution was the first in the world to protect equality regardless of sexual orientation. Raub says that shifted the public perception of LGBTQ people.

And even though such social change can take time, after South Africa adopted its new constitutional, the country moved quickly to legalized same-sex marriage, include LGBTQ people in military service, and ban conversion therapy. Another example is Mexico: A 2015 high court decision declared a ban on same-sex marriage unconstitutional, as the constitution forbids discrimination based on sexual orientation.