Year	gross (GPI)
1971	0.580829977989197
1972	0.583429992198944
1973	0.587679982185364
1974	0.586210012435913
1975	0.613200008869171
1976	0.644010007381439
1977	0.662310004234314
1978	0.678269982337952
1982	0.710810005664825
1983	0.735050022602081
1984	0.77250999212265
1985	0.795629978179932
1986	0.815119981765747
1987	0.822969973087311
1988	0.841759979724884
1989	0.860230028629303
1990	0.87720000743866
1991	0.89165997505188
1992	0.902350008487701
1993	0.912620007991791
1994	0.92085999250412
1995	0.922339975833893
1996	0.921249985694885
1997	0.926580011844635
1998	0.927919983863831
1999	0.937439978122711
2000	0.942369997501373
2001	0.944310009479523
2002	0.949859976768494
2003	0.9548299908638
2004	0.958509981632233
2005	0.966099977493286
2006	0.966989994049072
2007	0.972880005836487
2008	0.976760029792786
2009	0.976440012454987
2010	0.979009985923767
2011	0.979030013084412
2012	0.979839980602264
2013	1.01442003250122
2014	1.05037999153137
2015	1.06231999397278
2016	1.06938004493713
2017	1.05747997760773
2019	1.05552005767822
2020	1.06061995029449