Sample trajectories for the evolutionary dynamics in collective-risk dilemmas.

<p>(a) For small risk probability, , the initially random contributions quickly drop to zero. Consequently, the target is never met and the average payoff is 90% of the initial endowment, as expected. (b) For high risk probability, , strategies investing the target sum are favored. After a few generations, in the majority of games the target is met, leading to an average payoff of almost half of the initial endowment (parameters , , , , , , ).