As I noted in my initial presentation, there are really three factors at play when you open bidding up to competition. One is that, as the bidders increase, you have an incentive to try to beat your competitor. As there are more competitors, you are less able to anticipate the behaviour of somebody else. If you're regularly competing against the same two players, for instance, in the local environment, you may know that they're busy right now and aren't going to be able to handle it. So you're going to read their behaviour and bid slightly higher and deal with that accordingly.
But there are also times in the construction world where companies are what they call hungry. They want to keep their workforce employed because they know they have work two years down the road and they'll take a haircut on their profit to win. That's the second one. Then the third reason, of course, is that it does have the tendency to reduce collusion.