Year	gross (GPI)
1971	0.522159993648529
1972	0.530960023403168
1973	0.573310017585754
1974	0.544669985771179
1976	0.527069985866547
1978	0.533179998397827
1979	0.539860010147095
1980	0.536769986152649
1981	0.548089981079102
1982	0.549149990081787
1983	0.550979971885681
1984	0.55282998085022
1987	0.575030028820038
1988	0.570379972457886
1989	0.589569985866547
1990	0.583769977092743
1991	0.585460007190704
1992	0.572730004787445
1993	0.597809970378876
1994	0.610889971256256
1995	0.646740019321442
1996	0.638540029525757
1997	0.633120000362396
1998	0.665750026702881
1999	0.678139984607697
2000	0.703769981861115
2003	0.712300002574921
2004	0.734160006046295
2005	0.745739996433258
2006	0.758830010890961
2007	0.778299987316132
2008	0.782509982585907
2009	0.790750026702881
2010	0.807290017604828
2011	0.818239986896515
2013	1.00229322910309
2014	0.839339971542358
2015	0.864260017871857
2016	0.838020026683807
2017	0.868219971656799
2018	0.876399993896484
2020	0.898059785366058