Table 1.

Payoff matrix of the PGG

Contribution		Other
		0	1	2	3	4	5	6	7	8	9	10	11	12
	0	80	94	108	122	136	150	164	178	192	206	220	234	248
	1	85	99	113	127	141	155	169	183	197	211	225	239	253
	2	88	102	116	130	144	158	172	186	200	214	228	242	256
	3	89	103	117	131	145	159	173	187	201	215	229	243	257
Y	4	88	102	116	130	144	158	172	186	200	214	228	242	256
O	5	85	99	113	127	141	155	169	183	197	211	225	239	253
U	6	80	94	108	122	136	150	164	178	192	206	220	234	248
	7	73	87	101	115	129	143	157	171	185	199	213	227	241
	8	64	78	92	106	120	134	148	162	176	190	204	218	232
	9	53	67	81	95	109	123	137	151	165	179	193	207	221
	10	40	54	68	82	96	110	124	138	152	166	180	194	208
	11	25	39	53	67	81	95	109	123	137	151	165	179	193
	12	8	22	36	50	64	78	92	106	120	134	148	162	176

Each line corresponds to a possible contribution of the participant (YOU), columns are possible contributions of the partner (OTHER). The number in each cell denotes the payoff of the participant given both contributions. The standard Nash equilibrium is a contribution of 3 by both players, thus earning 131. The social optimum (Pareto optimal solution) is to contribute 10, with a payoff of 180.