If “Buying American” matters to you, Detroit offers some cars and truck models with the most U.S. parts and labor, even as the industry becomes ever-more global.

Three General Motors models — Buick Enclave, GMC Acadia and Chevrolet Traverse — were tied at the top the list of the most American-made car models in the 2017 Kogod Made in America Auto Index, as compiled by the business school at American University.

Next came Ford’s F-150 pickup truck, followed by another GM model, the Chevrolet Corvette.

The index works by taking into account several factors that go into the assembly of a car. This includes the percentage of U.S. or Canadian parts used, the location of the factory where the vehicle was assembled, the source of the engine and transmission and whether more than 15% of the parts came from a foreign country. Each category receives its own score.

Over the past five years since the index began, overall American content and labor in cars has been decreasing, finds Frank DuBois, a professor at American University’s Kogod School of Business, has been compiling the index. It’s down about five percentage points.  

“U.S. domestic companies are taking advantage of outsourcing,” DuBois said.  

Other cars that made the list include the Jeep Wrangler in fourth place, the Ford Expedition, Navigator and Taurus in fifth, two Cadillac cars tied with the Chevy Colorado pickup for sixth, the Jeep Cherokee, the Honda CRV, Pilot and Ridgeline in eighth, the Toyota Camry coming in ninth place and the Ford Explorer and Chevy Malibu Hybrid coming in at 10th place on the list.  

In tying for first place, the Enclave, Acadia and Traverse all received a score of 85.5.

The results were celebrated by a lobbying organization for Detroit’s Big 3 — GM, Ford and Fiat-Chrysler.

“America’s three auto manufacturers once again dominated,” said Matt Blunt, president of the American Automotive Policy Council. “(American University’s) research also found that American automakers are at the top of the list in producing trucks, sedans and SUVs with U.S. auto parts.”

In 2016, the auto industry supplied over 7 million jobs and sold 17.5 million vehicles. They comprised 3.5% of the nation’s gross domestic product. Some 65% of those vehicles were produced in the U.S., a slight increase over 2015 sales which broke a 15-year record, according to the Alliance of Automobile Manufacturers. 

DuBois said he considers his index to be the most accurate gauge of domestic content in vehicles because, among other reasons, he includes the estimated costs of research and development that goes into a model. Surveys differ. Cars.com, for instance, cited the Toyota Camry as the most American-made of cars in its annual survey last year.

But DuBois says he uses a different formula for his results.

“I wasn’t happy with some of the other indices out there,” DuBois said. “Some of the indices had just used the percentage of U.S. (and) Canadian parts content … so I said, ‘there has to be a better way.'”

DuBois said he uses publicly available data to develop the index. He pulled data from the American Automobile Labelling Act, automakers’ annual reports and corporate filings to the Securities and Exchange Commission.

The rankings, including ties: