The gripes that led United Technologies to consider moving its Carrier air conditioning manufacturing operations and 2,100 jobs from two Indiana factories to Mexico had more to do with regulations than with wages, according to an official letter disclosed on Dec. 27 in the Washington Post.

Last March, when the manufacturer's plans first became news, Sen. Joe Donnelly, D-Ind., had charged that "this is about Carrier chasing Mexican wages at $3 an hour."

But Jim Schellinger, president of the Indiana Economic Development Corporation, countered in the letter reported by the Post that "extensive federal regulations were the leading factor of the decision to relocate 2,100 manufacturing jobs." A copy of the letter was released as part of a public records request.

Trump, meanwhile, has promised to scale back regulation.

“Fifty-three new regulations,” Trump said in a Dec. 1 speech at Carrier's Indianapolis plant, repeating a figure that Robert McDonough, CEO of Carrier parent United Technologies, had used. “Massively expensive and probably none of them amount to anything in terms of safety. … Your unnecessary regulations are going to be gone.”

Neither Trump nor McDonough identified which regulations they think are hindering enterprise, but Carrier sent a list of Department of Energy efficiency rules to Schellinger, the Post reports.

While those federal regulations apply to any equipment sold in the U.S. regardless of its origin, a spokesman for the Air Conditioning Heating and Refrigeration Institute notes in the Post that manufacturers seek cheaper labor to offset the cost of regulatory compliance.