Table 1.

Notation for the model

Parameter	Definition
b	Benefit (per unit of collective investment) to the group from public goods
c	Cost (per unit of investment) to a player from public goods
N	Number of players in the group
${\omega }_i$	Fitness of the i th player
$p_i$	Frequency of the i th player
$x_i$	Investment strategy of the i th player
$x_G$	Collective investment of all players in the group
${\widehat{x}}_i$	Evolutionarily stable strategy (ESS) with respect to the i th player
n	Number of players in the group that contribute to public goods
$\overline{p}$	Average frequency of all contributing players in the group
${\widehat{x}}_G$	Coevolutionarily stable strategy (coESS) of collective investment by a group of players each pursuing the ESS