Year	gross (GPI)
1970	0.644699990749359
1971	0.644999980926514
1972	0.647589981555939
1973	0.663869976997375
1974	0.683539986610413
1975	0.719609975814819
1976	0.760439991950989
1977	0.794130027294159
1978	0.839940011501312
1979	0.867829978466034
1981	0.914210021495819
1982	0.937080025672913
1983	0.965690016746521
1985	0.994260013103485
1986	1.00216996669769
1987	0.993950009346008
1988	0.990819990634918
1989	0.984619975090027
1991	0.976999998092651
1992	0.967880010604858
1993	0.97010999917984
1994	0.977280020713806
1995	0.979669988155365
1996	0.983950018882751
1997	0.985949993133545
2010	0.978929996490479
2014	1.03181004524231
2015	1.04112994670868
2016	1.03751003742218
2017	1.03073000907898
2018	1.02789998054504
2019	1.03170001506805
2020	1.04066002368927
2021	1.04410994052887