It takes three agreements to make one agreement in collective bargaining because three different groups have to endorse any proposal before it can become a final contract. These groups are the management, the labor negotiating team, and the union membership.
Collective bargaining typically takes place between a negotiating team from the union and one from the company. These people are empowered to bargain, but they, particularly on the union side, do not have the authority to finalize an agreement. As the bargaining takes place, the first two agreements have to happen. The union negotiating team and the company’s negotiators each have to accept a proposal in order for it to go forward. At that point, there is still one more agreement that has to happen. We can assume that the company will agree to anything that its team has agreed to. However, this is not always the case with the union since union negotiators cannot put every part of an agreement to a vote of their membership as they try to hammer out the deal. Therefore, the third agreement has to come from the union membership. It has to vote to ratify the contract. This does not always happen. As an example, the article below tells us of an instance in 2013 when Boeing workers rejected a contract proposal that had been at least provisionally accepted by their union’s negotiating team.
Thus, it can take three agreements to make one agreement in the area of collective bargaining.