United Auto Workers (UAW) union member Maryo Mendez wears a costume and plants a sign in the back of his pickup truck at the UAW union hall in Fremont, California February 12, 2010 Robert Galbraith/Reuters Paul Krugman, the Nobel-winning economist and New York Times columnist, took to Twitter on Friday to address the state of the US labor market and President-elect Donald Trump's promises to bring back manufacturing jobs.

To Krugman, the decline in manufacturing employment in the US isn't because of outsourcing, but rather a decades-old feature of the industry.

"The story of US manufacturing is basically one of high productivity growth allowing demand to be met with ever fewer workers," Krugman wrote.

Krugman is essentially arguing that the manufacturing sector hasn't added jobs to the labor market in years past. Instead, improved equipment and automation has allowed US manufacturers to increase output. Thus even if manufacturing came back to the US, most of the plants would be automated anyway, producing a lower number of jobs than one might hope for.

The tweetstorm probably has something to do with Trump repeatedly promising throughout his campaign to bring manufacturing jobs back to the US. Even on Thursday, Trump tweeted that he was working with Carrier, the air conditioner maker, to keep its plant in Indiana.

As a counter to that, Krugman appears to be arguing that fighting to keep these jobs rather than pivoting toward the service sector is backward thinking.

"Nothing policy can do will bring back those lost jobs. The service sector is the future of work; but nobody wants to hear it," the economist wrote.

To Krugman's point, manufacturing employment peaked in 1979, before a significant number of the free trade agreements Trump blames for the decline.

Krugman has been active on Twitter following the election, bemoaning the loss of Democrat Hillary Clinton and criticizing the policies and appointments of Trump.

Here's the full Twitter argument: