Year	gross (GPI)
1971	0.763520002365112
1973	0.769500017166138
1974	0.773710012435913
1975	0.761520028114319
1976	0.753229975700378
1977	0.751460015773773
1978	0.752290010452271
1979	0.75654000043869
1980	0.765659987926483
1981	0.764840006828308
1982	0.764789998531342
1983	0.753489971160889
1984	0.748889982700348
1985	0.741339981555939
1987	0.755900025367737
1988	0.766080021858215
1989	0.776579976081848
1990	0.779609978199005
1995	0.842209994792938
1999	0.885079979896545
2000	0.895910024642944
2001	0.910210013389587
2002	0.912970006465912
2003	0.915970027446747
2004	0.906120002269745
2005	0.919409990310669
2006	0.938839972019196
2007	0.948660016059875
2008	0.952310025691986
2009	0.950110018253326
2011	0.958329975605011
2012	0.963100016117096
2013	0.967050015926361
2014	0.978120028972626
2015	0.981519997119904
2016	0.996119976043701
2017	0.99686998128891
2018	1.0022200345993
2019	1.00817000865936
2020	1.01235997676849