Year	gross (GPI)
1970	0.97325998544693
1971	0.972729980945587
1972	0.974370002746582
1973	0.981029987335205
1974	0.975329995155334
1975	0.976949989795685
1976	0.983399987220764
1977	0.976450026035309
1978	0.977400004863739
1979	0.976329982280731
1980	0.977840006351471
1981	0.978250026702881
1982	0.980870008468628
1983	0.982190012931824
1984	0.982119977474213
1985	0.983179986476898
1986	0.983380019664764
1987	0.984109997749329
1988	0.982800006866455
1989	0.984409987926483
1990	0.985530018806458
1991	0.986630022525787
1992	0.987879991531372
1993	0.988229990005493
1994	0.986259996891022
1995	0.984080016613007
1996	0.982400000095367
1997	0.982280015945435
1998	0.981040000915527
1999	0.981549978256226
2000	0.982100009918213
2001	0.983739972114563
2002	0.983820021152496
2003	0.986000001430511
2004	0.987049996852875
2005	0.986710011959076
2006	0.988550007343292
2007	0.989669978618622
2008	0.989719986915588
2009	0.991729974746704
2010	0.992969989776611
2011	0.99481999874115
2012	0.995609998703003
2013	0.99822998046875
2014	0.999180018901825
2015	0.999230027198792
2016	0.999339997768402
2017	0.996479988098145
2018	0.995260000228882
2019	0.996810019016266
2020	0.996779978275299