We knew General Motors' strategy for the tenth-generation Chevrolet Impala would be different when the big sedan was launched in 2013. No longer intended to be the fleet queen and a hugely discounted showroom sedan, the tenth-gen Impala moved upmarket.

Consequently, sales decreased and did so in dramatic fashion. The Impala's U.S. volume in 2014 was down by more than half compared with 2007 output. Sales continued to fall, with the Impala's 2016 calendar year result of 97,006 U.S. sales representing the sixth consecutive year of decline.

The Impala's numbers are getting lower. Much lower. After averaging more than 8,000 monthly Impala sales in 2016 and nearly 10,000 per month as recently as 2015, Impala volume has cratered in early 2017. Only 3,213 Impalas were sold in the United States in April 2017, down 73 percent compared with the Impala's April average over the last five years.

But don't assume the scarcity of Impala sales will translate to an abundance of deals at your local Chevrolet dealer. Impalas are thin on the ground, and GM isn't playing games with incentives.

"Many of our competitors are building large cars for practice. We are building them for profit," GM spokesperson Jim Cain (no relation) told TTAC yesterday.

Rather than chasing volume with the kinds of significant discounts FCA and Ford are using to move Chargers, 300s, and Tauruses, GM is attempting to protect residual values and thereby improve customer satisfaction in the long run.

This means the Impala is nowhere near as common today as it once was, not even remotely as common this year as last. Among mainstream brand full-size cars, the Impala's market share shrunk from 23 percent in 2016's first four months to 19 percent this year. The Impala was easily the segment leader at this time last year; now it's 4,000 sales back of the Dodge Charger.

But according to J.D. Power PIN data obtained by TTAC, there are key differences.

As a percentage of their average transaction prices, incentives on the Dodge Charger and Chrysler 300 in April stood at 21 percent and 31 percent, respectively. The Impala's average incentive as a percentage of its April average transaction price was just 12 percent. The new Buick LaCrosse, which is quickly becoming a truly uncommon car, was incentivized to the tune of just 13 percent. In the large car segment, only the Toyota Avalon's 7-percent average incentive as a percentage of ATP was lower.

Moreover, the Impala's average transaction prices are rising. Year-to-date, the few Impalas that are leaving Chevrolet showrooms are $600 more costly than they were a year ago. In the full-size segment, only the LaCrosse, Avalon, and Impala have seen average transaction prices rise. The Nissan Maxima, Ford Taurus, and Chrysler 300 have all seen their ATPs fall by more than $1,000.

Aside from the fresh-faced Maxima, newly launched for the 2016 model year, those cars are also suffering from declining sales. (Maxima volume is up 2 percent so far this year.) But their declines are not as severe as those experienced by the Impala and LaCrosse.

Meanwhile, the inventory glut that plagues GM, and GM's car division in particular, is not a problem that involves the Impala. According to Automotive News, GM has just a 19-day supply of Impalas in an industry that now has a 73-day supply of new vehicles.