Year	gross (GPI)
1970	0.994350016117096
1971	0.986850023269653
1972	0.982559978961945
1973	0.983990013599396
1974	0.97759997844696
1975	0.974430024623871
1976	0.977190017700195
1977	0.974389970302582
1978	0.971920013427734
1979	0.968869984149933
1980	0.966880023479462
1981	0.968289971351624
1982	0.956420004367828
1983	0.963729977607727
1984	0.961470007896423
1985	0.962679982185364
1986	0.961629986763
1989	0.97664999961853
1990	0.978940010070801
1991	0.978670001029968
1992	0.97460001707077
1993	0.977739989757538
1996	0.97078001499176
1997	0.973020017147064
1998	0.971819996833801
1999	0.9723299741745
2000	0.976080000400543
2002	0.976230025291443
2003	0.975059986114502
2004	0.954299986362457
2005	0.955619990825653
2006	0.955340027809143
2007	0.950900018215179
2008	0.948490023612976
2009	0.951759994029999
2010	0.971520006656647
2011	0.968299984931946
2012	0.96833997964859
2013	0.968739986419678
2014	0.96943998336792
2015	0.970149993896484
2016	0.970820009708405
2017	0.971580028533936
2018	0.971270024776459
2019	0.97189998626709
2020	0.967980027198792