Year	gross (GPI)
1977	1.31304001808167
1979	1.41846001148224
1983	1.0280100107193
1984	1.50547003746033
1986	1.14660000801086
1987	1.14280998706818
1992	1.3034600019455
1993	1.31581997871399
1994	1.3204699754715
1998	1.49697995185852
1999	1.53003001213074
2000	1.51012003421783
2001	1.47904002666473
2002	1.48359000682831
2003	1.51707005500793
2004	1.54576003551483
2005	1.555340051651
2006	1.54639005661011
2007	1.51485002040863
2008	1.53716003894806
2009	1.46955001354218
2010	1.4833699464798
2011	1.44578003883362
2012	1.44152998924255
2013	1.46237003803253
2014	1.43608796596527
2015	1.36715543270111
2016	1.36201393604279
2017	1.36288487911224
2018	1.3450413942337
2019	1.3547523021698
2020	1.3371000289917