The auto industry had a good year, showing sales growth even in the luxury vehicle segment, where many brands set sales records.

In spite of somewhat disappointing December numbers, auto sales totals in the United States were a "healthy return to normalcy," Yahoo! Autos reported.

The boost came from such factors as pent-up demand from the economic downturn, lower credit rates and new models, the outlet said. Carmakers and their dealerships sold around 15.6 million vehicles in 2013, rising about 8 percent from the year before.

Surprisingly, the heavy auto players weren't SUVs; instead, the biggest movers were luxury models from Cadillac and Lamborghini, Yahoo reported.

Some examples include BMW, which saw 10 percent growth; Rolls-Royce, which had a 60 percent jump in sales, and Lamborghini with a 33 percent sales increase.

"We're seeing much more confidence, with much more conviction among customers about the future of the economy, more optimism and enthusiasm," said Kevin Rose, sales and marketing director for Bentley Motors, which saw U.S. sales increases of 28 percent to 2,964 vehicles in 2013.

The two fastest-growing U.S. brands last year were Cadillac and Ram, according to Yahoo. Of all luxury brands, Ferrari was the only one to post a decline; the company recently announced it was limiting sales to keep its exclusivity.

So who is investing wealth into luxury vehicles and the auto industry? Wall Street, according to Yahoo.

"Stock-market gains often drive car sales at the high end, and in a year where Wall Street stock indexes had their best results in more than 15 years, it doesn't take much of that money to produce a waiting list at the luxury-car dealership," Yahoo said.

While rising interest rates may dampen enthusiasm for buying new car, the American auto industry should continue to rise next year as people continue to need replacements for older vehicles.

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