Unplanned pregnancies cost the U.S. over $5.5 billion in 2018 but sex education still leaves students with questions. Here's why.

The majority of U.S. students report they've had sex before graduation, which means the type of sex education they receive can be a big deal, for themselves personally and for the economy.

"[There's an] absurd and huge burden we put on sex ed that we don't put on other subjects," said Jonathan Zimmerman, author of the book Too Hot to Handle: A Global History of Sex Education and a professor at the University of Pennsylvania. "The algebra teacher is enjoined to teach them more algebra. Only in sex ed is the sex ed teacher enjoined to actually change how the kids behave out of school. And this may be an impossible burden."

Direct medical costs of unintended pregnancy in the United States totaled at least $5.5 billion in 2018, a rise from the 2011 estimate of $4.6 billion. Additionally, teenagers who unintentionally become pregnant tend to receive less education and are less likely to have a spouse with whom they can share the financial support of raising a child. The high cost of teen pregnancy may have even pushed Mississippi into legislating sex education requirements.

There's been a debate spanning decades about what information to include in the curriculum. Some argue adolescents should have access to comprehensive information around sexual health to make their own decisions, while others feel abstinence should be stressed so as not to encourage teenagers to engage in sexual activity.

A little more than half of states require students to receive some kind of sex education as well as HIV education, according to sex education advocacy group SIECUS. Only 18 states require plans to be medically accurate and 16 states require instruction on contraception.

The federal government doesn't have any official regulations for what schools must include in sex education curriculum. Instead, the government has enforced de facto policies through funding requirements. Federal funding for abstinence-only education increased in 2016. In 2015, the federal government provided about $55 million. In 2021, that number was up to $110 million.

Watch the video above to learn why sex education is so crucial for the economy and what happens when some students are left behind.