The single best sales month was December 2016.

There was a lot going on in 2016, not the least exciting of which was Nico Rosberg wining the F1 Championship. Automakers sold more vehicles in 2016 than they did at any other point during the decade. The December 2016 sales capped off a record year. Here's the top five months over the decade by volume:

• December 2016: 1,683,408
• March 2018: 1,648,222
• May 2015: 1,634,833
• December 2015: 1,634,329
• August 2019: 1,632,287

Subaru might have had the best decade of everyone.

Sure, Ford sold a lot of trucks and Nissan saw tremendous early-decade growth in its SUV lineup, but Subaru is the real winner. In 2010, Subaru sold 263,000 vehicles in the U.S. By the end of the decade, in 2019, they sold 700,000. They probably would have sold more but they scaled back production to launch two new vehicles at the end of the decade.

Most forecasts were wrong about December 2019, but that doesn't mean it was a great month.

Analysts forecasted weak sales for the last month of 2019 but the market surprised them delivering a strong result. However, December 2019 was only the 26th best-selling month of the decade according to KBB, which measured 1,506,401 units sold. See the best-selling trucks of 2019 here.

Volvo's best month was the last month of the decade.

Volvo left the decade with the best month it has had in 10 years. The company sold 12,360 units. However, Volvo had higher sales in the months prior to the Great Recession.

Ford delivered the highest monthly sales total of all automakers in the last 10 years.

While some may bemoan the Blue Oval's current state of automotive affairs, they had a really great month five and a half years ago. In May 2014, Ford sold 244,501 vehicles, roughly 15.5% of the entire industry's sales for the month. In that single month, Ford sold more vehicles than Smart did in the entire decade. See the best-selling new cars of 2019 here.

Buyers are spending more on their cars than ever before.

According to KBB, "At the end of 2011, the average transaction price (ATP) for a new vehicle in the U.S. was near $30,000. In February 2015, ATP for the month was above $33,000 for the first time ($33,056). It broke through $35,000 in June of 2017, and passed $37,000 later that year, in December when transaction prices commonly peak due to the high volume of luxury vehicle sales. Transaction prices were above $38,000 through the final three months of 2019. The Kelley Blue Book ATP in December 2019 was $38,767 – the highest point in the past decade."

See the best-selling new SUVs of 2019 here.

Tesla came to play.

In 2010 and 2011, Tesla wasn't really on anyone's radar and now it's a household name. KBB estimates that Tesla sold 12 vehicles in June 2012. They reached 10,000 in sales per month in March 2018 and hit peak monthly sales in December 2018 when 32,600 vehicles were sold.

High-performance cars were costliest in January 2019.

Everyone seems to drive a Toyota RAV4 or a Honda Civic. For the select few wealthy enough to enjoy the fruits of the Acura NSX, Ford GT, and anything with a horse logo on it, this decade was kind for options but expensive. KBB says that in January 2019, the ATP for the segment peaked for the decade at $121,739.

With the Trump Tax Cuts came more fleet sales.

According to KBB, "Six of the Top 10 best months for fleet sales in the past decade occurred after the Tax Cuts and Jobs Act of 2017. In May 2019, an estimated 425,000 vehicles were sold to fleet buyers, a record 27 percent of total U.S. sales. Fleet, it's worth noting, generally accounts for 20% of sales in a given month."

There was never a time in the last 10 years that the Ford F-Series was not the best-selling vehicle in the U.S.

Ten straight years of month-to-month dominance. Muhammed Ali wasn't even that good. Ford has sold 7,578,608 F-Series pickups in the last decade - one every 41 seconds. The best month for the F-Series was December 2017 where, in a single month, the company sold 89,385 F-Series trucks.