Year	gross (GPI)
1971	0.536350011825562
1972	0.532379984855652
1973	0.53532999753952
1974	0.543630003929138
1975	0.543169975280762
1976	0.537370026111603
1977	0.526430010795593
1978	0.515410006046295
1979	0.537559986114502
1980	0.511740028858185
1981	0.511150002479553
1988	0.521120011806488
1989	0.527620017528534
1990	0.528339982032776
1991	0.529950022697449
1992	0.545140027999878
1993	0.562839984893799
1996	0.598190009593964
1997	0.612139999866486
1998	0.625339984893799
1999	0.639919996261597
2000	0.64683997631073
2001	0.654449999332428
2002	0.656790018081665
2003	0.668110013008118
2004	0.67289000749588
2005	0.688790023326874
2006	0.69666999578476
2007	0.711269974708557
2008	0.744579970836639
2009	0.759230017662048
2010	0.789359986782074
2011	0.79448002576828
2012	0.810209989547729
2013	0.814520001411438
2014	0.826129972934723
2015	0.824790000915527
2016	0.831380009651184
2017	0.838320016860962