ROUND UP THE USUAL ALGORITHMS!

Apparently algorithms to play prisoners' dilemma games are becoming subtle.  The Grim Strategy is apparently a blunt instrument for humans with long memories.  "Our findings suggest that in this framework even relatively simple pricing algorithms systematically learn to play sophisticated collusive strategies. The strategies mete out punishments that are proportional to the extent of the deviations and are finite in duration, with a gradual return to the pre-deviation prices."  Might make for interesting times, both in antitrust enforcement and in teaching industrial economics.