Year	gross (GPI)
1970	0.913010001182556
1971	0.896700024604797
1972	0.930230021476746
1973	0.921410024166107
1974	0.947130024433136
1975	0.952989995479584
1976	0.942300021648407
1977	0.946049988269806
1978	0.944599986076355
1979	0.949039995670319
1980	0.951290011405945
1981	0.953639984130859
1982	0.957740008831024
1983	0.958739995956421
1984	0.962379992008209
1985	0.966109991073608
1986	0.969399988651276
1987	0.968699991703033
1988	0.969430029392242
1989	0.971949994564056
1990	0.974680006504059
1991	0.971750020980835
1992	0.965040028095245
1993	0.965260028839111
1994	0.966629981994629
1995	0.974120020866394
1996	0.972069978713989
1997	0.971840023994446
1998	0.980409979820251
1999	0.978860020637512
2000	0.973029971122742
2001	0.981700003147125
2002	0.984520018100739
2003	0.981509983539581
2004	0.977249979972839
2005	0.98470002412796
2006	0.981630027294159
2007	0.980300009250641
2008	0.987909972667694
2009	0.983709990978241
2010	0.988359987735748
2011	0.987760007381439
2012	0.989549994468689
2013	0.990989983081818
2014	0.981710016727448
2015	0.984409987926483
2016	0.984650015830994
2017	0.984489977359772
2018	0.982209980487823
2019	0.979749977588654
2020	0.98198002576828