The National Safety Council says that 433 people will die in car crashes over the Thanksgiving holiday and that 52,300 more will be seriously injured. It’s safe to assume that some of the dead and injured will be back-seat passengers who opt not to wear seat belts.

The council’s holiday projections coincide with a report that says 883 back-seat passengers who weren’t wearing seat belts died in car crashes in 2013. And a third release of data — this for 2014 — says that 10,300 people who died either in the front or back seat were not wearing seat belts.

“Seat belts save lives,” said Mark Rosekind, administrator of the National Highway Traffic Safety Administration. “It’s the number one safety technology we have available. It doesn’t matter where you are in a vehicle, you should wear your seat belt.”

An estimated 87 percent of Americans wear seat belts, but the number of people who wear them when riding in the back seat drops by nine percentage points, according to a study released this week by the Governors Highway Safety Association. People seem particularly prone to ignore the belt when riding in taxicabs.

“Too many adults mistakenly believe that they are somehow magically protected in the back seat when they get into a for-hire vehicle,” said Jonathan Adkins, executive director of GHSA, an organization of state highway-safety officials. “Convincing adults to buckle up, every trip, in every seat, will require a concerted effort among lawmakers and highway-safety professionals.”

The GHSA report was authored by James Hedlund, a former official at NHTSA.

“Families traveling together at the holidays often means adults sitting in the rear seats, where they might not be accustomed to buckling up in the same way they are when they get in the driver’s seat,” Hedlund said.

In making its grim forecast of deaths and injuries during the four-day holiday weekend, the NSC estimated that 164 lives may be saved this holiday because of seat belt use.

Twenty-two states, including Virginia, don’t require back-seat passengers to use seat belts. In 15 states, seat belt laws are secondary enforcement, so an officer must stop a driver for an unrelated infraction to write a seat belt ticket. Four states that mandate use of seat belts in the rear seats — Maryland, Illinois, Vermont and Wisconsin — exempt taxis and other vehicles for hire, such as those used by Uber and Lyft.

The GHSA report points to two high-profile cases in which back-seat passengers died when not belted. CBS newscaster Bob ­Simon died this year when he was riding in a limousine in Manhattan, and Nobel Prize winner John F. Nash Jr. and his wife were killed in a crash on the New Jersey Turnpike.

In reviewing the 2013 fatal crashes in which unrestrained passengers were killed, GHSA found that 473 involved cars, 244 were in SUVs, 68 were in vans and 98 were in pickup trucks. Two were in taxis.

The other data set released Tuesday came from NHTSA, which gathers and releases traffic fatality records each year. The federal agency said that 21,022 of the 32,675 people who died in crashes on U.S. roadways in 2014 were drivers or passengers inside vehicles. (Others were motorcyclists, pedestrians and bicyclists.) NHTSA said that 49 percent of those fatalities were people not wearing seat belts.

“We’d love to see primary seat belt laws for front- and back-seat passengers across the nation,” Rosekind said. “That has been a focus of NHTSA’s forever.”