Year	gross (GPI)
1971	0.382600009441376
1972	0.356669992208481
1973	0.367749989032745
1974	0.358579993247986
1975	0.362210005521774
1976	0.376929998397827
1977	0.374689996242523
1978	0.363669991493225
1979	0.334540009498596
1980	0.344669997692108
1981	0.365889996290207
1988	0.390630006790161
1989	0.390410006046295
1990	0.375539988279343
1991	0.381199985742569
1992	0.40472999215126
1993	0.457630008459091
1996	0.519289970397949
1997	0.54093998670578
1998	0.563549995422363
1999	0.590290009975433
2000	0.605260014533997
2001	0.611800014972687
2002	0.602639973163605
2003	0.616100013256073
2004	0.60903000831604
2005	0.627919971942902
2006	0.625549972057343
2007	0.622009992599487
2008	0.621540009975433
2009	0.622569978237152
2010	0.698220014572144
2011	0.6666100025177
2012	0.693979978561401
2013	0.705749988555908
2014	0.731599986553192
2015	0.735769987106323
2016	0.753069996833801
2017	0.747870028018951