The background, from Cox Automotive chief economist Jonathan Smoke, on the eve of this week's North American International Auto Show in Detroit:

• The U.S. auto industry sold 17.2 million cars and light trucks in 2018 — the fourth-best year in history — and higher than most economists predicted.
• The biggest reason for the missed forecasts: They underestimated how flush Americans would feel after Congress passed a massive tax cut in 2017.
• Businesses also bought more vehicles for their corporate fleets, taking advantage of lower tax rates.

What's happening: Some consumers may be surprised to learn they are receiving no tax refund in 2019, a smaller one than expected or that they might even owe the government money, says Smoke.

Details:

• More than 102 million Americans received an average tax refund of almost $2,800 last year.
• When the new tax law took effect in early 2018, the IRS and Treasury Department rushed to change the tax tables, but many Americans failed to check the IRS withholding calculator and adjust their W-4 forms.
• In July, the government warned that 30 million Americans were not withholding enough for taxes, meaning they felt richer than they were.

The problem could snowball if the government tries to fix hastily-made changes to the tax tables by over-correcting to withhold more money in future years, Smoke argues. In that case, consumers would see a decline in their net pay, cutting their spending power throughout the year.

• "If we are correct, it’s a double whammy," says Smoke.

Yes, but: Tax reform isn't the only reason auto sales are likely to decline this year. Vehicles are becoming less affordable, due to tariffs on steel and other commodities, rising interest rates and the cost of premium features and technology.

The bottom line: Cox Automotive, the digital information giant behind AutoTrader, Kelly Blue Book and Manheim Auto Auctions, sees U.S. auto sales falling to 16.8 million units in 2019.

Go deeper: Electric vehicles surge but falling short of long-term global target

The background: Under Barra, GM pulled out of unprofitable markets like Europe and redirected investments toward new technologies, like electric cars and automated vehicles.

• She stood up to President Trump, who blasted GM for its decision to close 5 factories — 4 of them in the U.S. — and cut almost 15,000 jobs. Barra reiterated her position today in a meeting with investors in New York.

What's new: GM said it finished 2018 stronger than expected, and signaled 2019 will be even better, the opposite of what the rest of the industry is signaling.

• 2019 adjusted earnings will be $6.50 to $7 a share, higher than analyst estimates.
• Profits from new pickups and SUVs will offset flattening sales in the U.S. and China.
• Cost cuts in engineering and manufacturing will help fund its push into electric vehicles.

What's next: Besides its continued focus on trucks, 3 new product lines will help lead GM into the future.

• Cadillac will be GM's new electric vehicle brand, leading an onslaught of 20 new EVs by 2023, many of them in China.
• A new family of Chevrolet vehicles, part of a $5 billion bet on global emerging markets, launches in China this year, then South America and Mexico.
• Cruise Automation, GM's self-driving car unit, expects to deploy a commercial robo-taxi service in San Francisco in 2019, then scale rapidly.

Why it matters: The auto industry is undergoing an awkward transition, caught between the decline of trusted business models and the lure of an uncertain future in which cars run on electrons (not gasoline), are shared (not owned) — and where driving is optional.

• The pressure has already resulted in GM plant closings and layoffs in North America and Ford cutbacks in Europe, with more bad news likely as the industry grapples with excess factory capacity worldwide.
• Some companies are pooling their efforts on AVs and electric vehicles, like GM and Honda. Ford and Volkswagen are expected to announce such an alliance next week.
• But that future isn't getting any closer. Bold predictions by Tesla and others that cars would be able to drive themselves by now have evaporated in the face of technology challenges and market realities.
• The timeframe for commercializing driverless cars is now said to be 2020–2021, but even that is unclear.
• "It seems like we’re kind of stuck where we are," says Eric Paul Dennis, who's been tracking AV promises made — and broken — since 2013 as a senior transportation systems analyst at the Center for Automotive Research.

Investors don't like uncertainty, which helps explain why GM, Ford and Fiat Chrysler stocks are down substantially. And for the time being, Wall Street is likely to focus on troubles confronting their core business (Auto 1.0), not the sexy stuff (Auto 2.0).

What’s happening: The annual Detroit auto show is looking to be the quietest since the depths of the 2009 recession, with fewer exhibitors and a shorter media preview.

• European luxury carmakers Audi, BMW and Mercedes-Benz aren't even showing up, following Jaguar-Land Rover and Porsche, which pulled out years ago.
• Audi and Mercedes had splashy car reveals last week in Las Vegas at CES, the tech show that has been siphoning attention away from Detroit for years.
• That competition — and the lousy weather in January — prompted show organizers to move the event to June starting in 2020. That lame duck status may be contributing to this year's blah-ness.

Yes, but: There will still be some notable vehicle debuts in Detroit next week, including new sports cars like the Toyota Supra and Mustang GT500, and crossover SUVs including the new Cadillac XT6, Kia Telluride and Ford Explorer.

• Future mobility tech is still relegated to the basement of Detroit's Cobo Center, where the Automobili-D conference and exhibition will be held for the third year.
• 65 startups from 10 countries — 20% more than last year — will participate, showing tech on everything from AVs to smart cities.