“The trend in manufacturing in the United States is to source domestically,” Harry Moser, the founder of the Reshoring Initiative, told Knowledge@Wharton. “With 3 to 4 million manufacturing jobs still off shore, we see huge potential for even more growth.” Decades after NAFTA, economists are asking—will this new, giant trade deal endanger the manufacturing gains of recent years?

“That trickle of jobs moving back that I think is going to grow into a bigger trickle: This is a speed bump for it,” said Wally Hopp, a professor at the University of Michigan’s Ross School of Business, said about the TPP. “At least certain products are going to suffer from it—with the tariff situation, all of a sudden, it’s easier to stay offshore.”

U.S. Manufacturing Jobs, in Thousands

Bureau of Labor Statistics

The nitty-gritty details of the TPP are still not public, but it’s known that the agreement seeks to gradually reduce trade barriers such as tariffs among member countries, which include Japan, Vietnam, and Malaysia. It adds intellectual property protections for certain products, including pharmaceuticals. It does not include rules on currency manipulation, which had disappointed some groups, because currency manipulation allows countries such as China to ensure that their goods are cheaper than U.S.-made goods. (Some economists believe that currency-manipulation provisions could make it more difficult for the U.S. to control its own currency and interest rates.) Hillary Clinton, who had formerly supported the TPP, said Wednesday on PBS NewHour that she opposed the pact because of the lack of currency manipulation rules and because of the sweet deal it gives to pharmaceutical companies. The deal also does not include China, the world’s second-largest economy, but is instead meant to increase the U.S.’s clout in Asia and make it easier to compete with China.

“Expanded trade through these agreements will contribute to higher incomes and stronger productivity growth over time in both the United States and other countries,” wrote a handful of economists, including Alan Greenspan and Ben Bernanke, in a letter to Congress. U.S. businesses will be able to sell more in overseas markets, the economists argue, and U.S. consumers will be able to have access to more affordable goods.

But trade agreements, at their heart, create winners and losers, and the TPP will likely create some U.S. manufacturing losers at a time when economists worry that the country is becoming too service-oriented. Fine wines and beef products made in the U.S. that currently have high tariffs in foreign countries might do well under the TPP, but agriculture doesn’t create many good jobs in the U.S. Automakers, on the other hand, could suffer. The TPP could take tariffs off of foreign-made small trucks, which are currently the big profit makers for the domestic automakers, said Art Schwartz, a former GM negotiator who is now president of Labor and Economics Associates. The deal may also make it more difficult for unions—especially the United Auto Workers—who are negotiating contracts with the Big Three: If automakers can say they have to outsource to compete, unions will have less leverage.

NAFTA led to some auto job losses and accelerated the shift of low-skilled factory jobs to Mexico, said Hopp. Companies either automated operations or moved them to somewhere that labor was cheaper when tariffs went away. Foreign direct investment in Mexico tripled as a share of that country’s GDP since NAFTA, according to Scott. Companies such as Whirlpool and virtually every U.S. automaker have moved some operations there. Even now, companies are moving auto production to Mexico.