Another point of discussion is the proportion of trade unionists. Opponents say that after the PLA, business leaders must hire their workers through unions and unionized workers are the majority of those working on PLA projects, although non-unionized workers make up the majority of construction workers.  Estimates of the proportion of non-unionists cited by PLA opponents are about 85%, based on figures from the Us Department of Labor Bureau of Labor Statistics and more recent data put the figure at 86.9%.  This figure is disputed by Denas, who indicates that the figures of opponents of the PLA are misleading and are based on census data that included an overly broad concept of a construction worker.  According to a 2010 Cornell University study cited by Mary Vogel, Executive Director of the Construction Institute, 60% of construction trades are unionized in Massachusetts.  Since its inception in 1998, The Construction Institute, a non-profit organization, has focused on the needs of the construction union sector in Massachusetts. “Taxpayers cannot get the best product at the best price of responsible contractors if the government takes special interests into account by appointing AEPs that control contracts to unionized companies. This creates a labor monopoly for unionized workers, who make up about a quarter of Missouris` private construction workers and only 14 percent of the construction industry nationally,” said Ben Brubeck, ABC`s vice president of regulation, Laboratory and State Affairs. “As Congress and the Trump administration consider a billion-dollar infrastructure proposal, they should follow the example of Missouri and 22 other states by immediately adopting a similar policy that maximizes competition, reduces costs and ensures the fiscal responsibility that taxpayers earn in federal and federal projects.” The measure prohibits municipalities and counties from requiring union working conditions for public projects funded in part by the state and uses “project work agreements.” The measure threatens municipalities that do so with the loss of financial resources and government tax credits. AFL-CIO officials said such agreements protected public investment with qualified contractors and kept projects with fewer injuries or labour disputes on time. Under the current system, union and non-union contractors could propose public projects, but in cases where such agreements were in place, non-union contractors were not obliged to engage in collective bargaining. PL`s can also influence competition by discouraging non-union offers, as evidenced by studies conducted by Ernst and Young in September 2001 on behalf of Erie County, New York.
This study analyzed the impact of AEPs on public works and concluded that the number of bidders for projects with a PLA has been reduced, as “the use of PLA severely impedes the participation of non-union contractors in public procurement.”  The Worcester Municipal Research Bureau prepared a report in 2001 based on a series of studies on the use of PLA.