Three things likely sparked this manufacturing jobs spike.
First, eight years of the Obama Administration’s piling on regulation upon regulation, from labor rules, to the Clean Power Plan, to the implementation of ObamaCare, placed industry into a defensive crouch. Business leaders were fearful of investing capital, not knowing how the federal rules might capriciously change, thus wiping out their expected return on investment.
That defensiveness ended in November 2016 when the expectations of additional regulatory burdens under a prospective President Clinton vanished. Not coincidentally, manufacturing employment started its sustained upswing the very month of Krugman’s tweet.
Second, the Trump Administration’s deregulatory practice exceeded expectations, with red tape being cut at a faster clip than achieved under President Ronald Reagan 36 years earlier.
Third, with the Republican Congress, President Trump delivered on a major overhaul of the tax code, including a significant cut to business taxes as well as a change to the treatment of overseas profits that incentivized the repatriation of some $300 billion in the first quarter of 2018 out of what the Federal Reserve estimates is $1 trillion in multinational profits held abroad.
Whether this manufacturing jobs boom will continue is now largely dependent on the Trump Administration’s high-stakes trade stand-off with the People’s Republic of China.