Year	gross (GPI)
1970	0.983500003814697
1971	0.965439975261688
1972	0.99330997467041
1973	0.964990019798279
1974	0.977689981460571
1975	0.978299975395203
1976	0.971560001373291
1977	0.968010008335114
1978	0.974399983882904
1979	0.969579994678497
1981	0.966130018234253
1982	0.955990016460419
1983	0.957159996032715
1984	0.96995997428894
1985	0.988030016422272
1986	0.976989984512329
1990	0.994239985942841
1991	0.995280027389526
1992	1.0050300359726
1993	1.00573003292084
1994	0.981959998607636
1995	0.988610029220581
1996	0.972530007362366
1997	0.955309987068176
1998	0.950389981269836
1999	0.949100017547607
2000	0.945439994335175
2001	0.96110999584198
2002	0.955099999904633
2003	0.946560025215149
2004	0.95032000541687
2005	0.970610022544861
2006	0.963940024375916
2007	0.962989985942841
2008	0.954949975013733
2009	0.984350025653839
2010	0.980849981307983
2011	0.983870029449463
2012	0.989939987659454
2013	0.999989986419678
2014	0.995289981365204
2015	0.994289994239807
2018	0.990289986133575
2019	0.973100006580353
2020	0.9548100233078