President Donald Trump’s import tariffs to protect and boost U.S. manufacturers backfired and led to job losses and higher prices, MarketWatch reported Friday.

Citing a Federal Reserve study, economists found the tariffs reduced competition for some industries in the domestic U.S. market — but that it was more than offset by the effects of rising input costs and retaliatory tariffs.

“We find that the 2018 tariffs are associated with relative reductions in manufacturing employment and relative increases in producer prices,” concluded Fed economists Aaron Flaaen and Justin Pierce, in their academic paper.

“[T]he longer-term effects of the tariffs may differ from those that we estimate here,” the economists conceded, but added: “[T]he results indicate that the tariffs, thus far, have not led to increased activity in the U.S. manufacturing sector.”

Tit-for-tat trade retaliation is an idea best relegated to the past, given the presence of globally interconnected supply chains, the Fed researchers found.

According to the report, the top 10 manufacturing industries hit by foreign retaliatory tariffs were producers of: magnetic and optical media, leather goods, aluminum sheet, iron and steel, motor vehicles, household appliances, sawmills, audio and video equipment, pesticide, and computer equipment.