Year	gross (GPI)
1971	0.987399995326996
1972	0.997290015220642
1973	0.996370017528534
1974	0.98759001493454
1975	0.945649981498718
1976	0.925230026245117
1977	0.930299997329712
1978	0.929400026798248
1979	0.9307000041008
1980	0.927879989147186
1981	0.946529984474182
1982	0.941699981689453
1983	0.950909972190857
1984	0.951290011405945
1985	0.943870007991791
1986	0.822560012340546
1988	0.912590026855469
1993	0.979189991950989
1994	0.928520023822784
1995	0.917519986629486
1996	0.969889998435974
1997	0.983430027961731
1998	0.92519998550415
1999	0.967019975185394
2000	0.963460028171539
2001	0.948629975318909
2002	0.949949979782104
2003	1.00172996520996
2004	0.965269982814789
2005	0.971029996871948
2007	0.977869987487793
2008	0.940959990024567
2009	0.934279978275299
2010	0.956279993057251
2011	0.944685339927673
2013	0.956330001354218
2014	0.981710016727448
2015	0.964420020580292
2016	0.969479978084564
2017	0.952560007572174
2018	0.984589993953705