Year	gross (GPI)
1971	0.434509992599487
1972	0.441969990730286
1974	0.451700001955032
1984	0.606679975986481
1991	0.695349991321564
1992	0.759679973125458
1993	0.745239973068237
1994	0.675379991531372
1995	0.63603001832962
1996	0.605080008506775
1999	0.622940003871918
2000	0.657270014286041
2001	0.687569975852966
2002	0.697749972343445
2003	0.69989001750946
2004	0.735090017318726
2005	0.782710015773773
2006	0.814249992370605
2007	0.836409986019135
2008	0.862770020961761
2009	0.892180025577545
2010	0.901250004768372
2011	0.912249982357025
2012	0.922720015048981
2013	0.928791224956512
2014	0.931964814662933
2015	0.921459972858429