Both versions of the PD situation above are two-player games. However, both
games are capable of being extended to include more than two parties. This
tends to increase the likelihood of defection, particularly in the ‘one-off’
situation. Such a situation is sometimes referred to as ‘the tragedy of the
commons’. The reasoning is that with more players it is important to defect
before others do; only if defectors are easily detected and punished will this be
prevented. Again this has important implications for oligopoly, as seen in the
last chapter. It is also relevant in international relations. The depletion of fish
stocks in the North Sea due to overfishing, and the resulting conflicts, are an