The total bankroll winner determination rule encourages competitors to submit agents that can do one thing: maximize their total winnings across all opponents.
Under the total bankroll winner determination rule, we are trying to isolate which agents are capable of maximally exploiting other agents submitted to the competition. Thus, under this winner determination rule, agents will be ranked based on total number of chips won against all competitors. That is, the player with the highest total bankroll wins the competition.
The biggest issue with determining the winner based on total bankroll is collusion. In particular, there is a concern that "anti-competitors", competitors that intentionally play poorly when they receive a particular signal, could be submitted. Or, multiple submissions may be made by the same group of people with one program having a model of the other program. All such behavior is considered to be against the rules. In previous years' competitions, measures were taken to prevent this kind of malicious agent from affecting the results. Recently the competition has taken an optimistic view that no such entries will be submitted. If an entry is suspected of violating the spirit of the competition, that entry will be subject to disqualification, as determined solely by the Arbiter.