(NewsNation) — For most of the 20th century, Americans could expect to live longer than those who came before them but that’s not the case anymore. Now, the U.S. life expectancy is in decline and the problem is increasingly a crisis of the young.

Today, one in 25 American five-year-olds won’t make it to their fortieth birthday, a recent Financial Times analysis found. That’s about one child in every kindergarten class.

Between 2019 and 2021, mortality rates for children and teenagers in the U.S. rose by nearly 20%, according to an analysis published in the Journal of the American Medical Association (JAMA) in March. Most of that increase had little to do with the pandemic.

“It turns out that COVID-19 had a marginal role to play in explaining this,” said Dr. Steven Woolf, Director Emeritus of the Center on Society and Health at Virginia Commonwealth University and author of the JAMA essay.

Woolf said the increase has been driven by four causes: suicides, homicides, drug overdoses and car accidents.

Firearms are now the leading cause of death for children and teenagers, accounting for almost half of the mortality increase in 2020. More than four times as many 1 to 19-year-old’s died by homicide as from COVID-19 in 2021, Woolf found.

There’s been a similar spike in drug overdose deaths, which increased 109% among 10 to 19-year-old’s from July 2019 to Dec. 2021. Of those, 90% involved opioids like fentanyl.

After declining over two decades, transportation deaths for children and teenagers have also increased. Since 2020, more than five times as many kids have died from car crashes and other transportation accidents as from COVID-19.

The rise in child and adolescent mortality is concerning on its own, but the primary causes paint an even darker picture. More American children are dying despite widespread advances in pediatric medical care and safety improvements to cars and buildings.

“The number of children and teenagers dying from these causes is so massive that it’s now outnumbering all of the lives saved in all of those other areas of progress,” Woolf said.

The worrying trend among today’s youth has drawn attention to one of the bleaker forms of American exceptionalism.

Since 1980, the U.S. life expectancy has increased slower than comparable developed countries like Australia, Canada, Germany and Japan. By 2010, the U.S. life expectancy had plateaued at 78.8 years before falling to 76.1 in 2021.

Much of that decline — particularly among older adults — is due to the pandemic, but while countries in western Europe have largely bounced back, the U.S. outlook has only gotten worse.

Today, the U.S. ranks last in life expectancy among G7 countries and 53rd in the world, according to a recent study. By comparison, the U.S. was third among G7 nations and 13th in the world in 1950.

The declining life expectancy has been driven almost entirely by a rise in deaths among males. Black youths have been hit especially hard by homicides and made up two-thirds of victims aged 10-19 years old, Woolf found. Their homicide rate is more than 20 times as high as white children and teenagers.

Historically, white adolescents have died at higher rates from drug overdoses than other racial groups but that gap closed in 2020. Transportation deaths were highest among Native American youth.

Woolf says more research is needed to determine which areas of the country have been most impacted but based on current trends he thinks more mental health resources and limiting children’s access to firearms will be crucial.

“A child’s chance of reaching age 20 is now falling in the United States,” he said. “When things reach that point it’s really frustrating to not take some kind of action.”