Black women in the U.S. are, on average, six times more likely to be murdered than white women, researchers wrote Thursday in The Lancet.

Why it matters: The study — which covered more than two decades — is the first to break out homicide trends among women between ages 25 and 44, when they are statistically more likely to be murdered.

• It's further evidence of how the lives of Black women are disproportionately threatened by systemic public health threats, including gun violence.

What they're saying: "To uncover the fact that Black women are murdered at rates as high as 20-to-1 is heart-breaking and underscores the urgent need to make substantive structural shifts," said lead author Bernadine Waller, a postdoctoral research fellow at Columbia University Irving Medical Center.

Details: The study drew on Centers for Disease Control and Prevention data covering nearly 32,000 murders of women that occurred between 1999 and 2020. It included data from 30 states that had a sufficient number of homicides for analysis.

• In 1999, the homicide rate among Black women was 11.6 per 100,000, compared with 2.9 per 100,000 for white women.
• While there was a temporary drop in 2013, to 7.2 per 100,000 Black women, the rate rebounded to 11.6 per 100,000 in 2020, compared with 3 per 100,000 for white women.

Zoom in: The greatest regional inequity was found in the Midwest, where Black women were 12 times more likely to be murdered than white women.

• The study also found Black women were also more likely to be killed by a gun. In the Northeast, in particular, researchers found Black women were six times likelier to be slain with a gun.
• The greatest difference at the state level was seen in Wisconsin where Black women were 20 times more likely to be murdered than white women in 2019 and 2020.
• States with the greatest racial inequities in homicide rates correlated with areas with the most "substantial structural inequities" when it came to wealth, researchers wrote.
• They also had enduring histories of slavery and lynching, and were where racially charged Black Lives Matter protests occurred during the COVID-19 pandemic, the researchers wrote.