Year	gross (GPI)
1974	0.903949975967407
1975	0.899429976940155
1977	0.931779980659485
1978	0.958369970321655
1979	0.977360010147095
1980	0.974609971046448
1981	0.964179992675781
1982	0.955720007419586
1983	0.940439999103546
1984	0.965040028095245
1985	0.965420007705688
1986	0.979149997234344
1987	0.976000010967255
1988	0.98650997877121
1989	0.986450016498566
1990	0.975189983844757
1991	0.997370004653931
1994	0.976069986820221
1998	0.974569976329803
1999	0.968069970607758
2000	0.979130029678345
2001	0.979099988937378
2002	0.975820004940033
2003	0.963169991970062
2004	0.959839999675751
2005	0.957419991493225
2006	0.958869993686676
2007	0.944329977035522
2008	0.938030004501343
2009	0.927709996700287
2010	0.929300010204315
2011	0.925750017166138
2012	0.921400010585785
2013	0.926639974117279
2014	0.925050020217896
2015	0.931389987468719
2016	0.932200014591217
2017	0.932910025119781
2018	0.934210002422333
2019	0.942239999771118