DETROIT — J.D. Power’s 2016 U.S. Initial Quality Study showed the largest improvement in seven years, with new-vehicle quality improving 6%. That’s more than double last year’s 3% improvement.

Now it in its 30th year, the study examines problems experience by vehicle owners during the first 90 days of ownership. Initial quality is determined by the number of problems experience per 100 vehicles (PP100), with a lower score reflecting higher quality.

According to this year’s study, quality improved across all eight problem categories measured, with 21 of the 33 brands included in the study improving their quality this year and one remaining the same.

“Manufacturers are currently making some of the highest quality products we’ve ever seen,” said Renee Stephens, vice president of U.S. automotive quality at J.D. Power. “Tracking our data over the past several years, it has become clear that automakers are listening to the customer, identifying pain points and are focused on continuous improvement. Even as they add more content, including advanced technologies that have had a reputation for causing problems, overall quality continues to improve.”

For the second time in the 30-year history of the study, U.S. domestic brands collectively showed lower problem levels than all their import counterparts combined. All three U.S. domestic brands posted year-over-year improvement, with the Detroit Three increasing their combined average by 10% from a year ago to 103 PP100.

And for the first time since 2006, non-premium brands showed fewer problems (104 PP100) than premium brands (108 PP100). Leading the way was Kia with a score of 83 PP100; the first time in 27 years a non-premium brand topped the rankings. It was also the second consecutive year that Kia, which ranked second in 2015, has led non-premium makes in initial quality.

Porsche ranked second with 84 PP100, followed by Hyundai with 92 PP100, Toyota with 93 PP100, and BMW with 94 PP100. Showing the most improvement were Chrysler and Jeep, with each reducing the number of problems by 28 PP100 from 2015.

Additionally, General Motors received seven model-level awards, following by Toyota Motor Corp. with six and Hyundai Motor Co. and Volkswagen with four each.

• General Motors models that ranked highest in their respective segments were the Buick Cascada; Chevrolet Equinox; Chevrolet Silverado HD; Chevrolet Silverado LD; Chevrolet Spark; Chevrolet Tahoe; and GMC Terrain.

• Toyota Motor Corp. models that ranked highest in their segment were the Lexus CT; Lexus GS; Scion tC; Toyota Camry; Toyota Corolla; and Toyota Highlander.

• Hyundai Motor Co. models that ranked highest in their segment were the Hyundai Accent; Hyundai Azera; Kia Soul; and Kia Sportage.

• Volkswagen AG models that ranked highest in their segment were the Audi Q3, Audi TT, Porsche Macan and Porsche 911.

The 2016 U.S. Initial Quality Study is based on responses from more than 80,000 purchasers and lessees of new 2016 model-year vehicles surveyed after 90 days. The study is based on a 233-question battery organized into eight problem categories.