Year	gross (GPI)
1981	0.969330012798309
1982	0.969990015029907
1983	0.971010029315948
1984	0.970969974994659
1985	0.970139980316162
1986	0.969669997692108
1987	0.970179975032806
1988	0.970430016517639
1989	0.970269978046417
1990	0.97146999835968
1991	0.972699999809265
1992	0.973630011081696
1993	0.969780027866364
1994	0.973100006580353
1995	0.971549987792969
1996	0.973640024662018
1997	0.975350022315979
1998	0.97010999917984
1999	0.964470028877258
2000	0.967100024223328
2001	0.95864999294281
2002	0.955320000648499
2003	0.948570013046265
2004	0.956219971179962
2005	0.957790017127991
2006	0.962050020694733
2007	0.963649988174438
2008	0.968569993972778
2009	0.975939989089966
2010	0.973299980163574
2011	0.97122997045517
2012	0.978399991989136
2013	0.980270028114319
2014	0.98131000995636
2015	0.9826700091362
2016	0.98430997133255
2017	0.975939989089966
2018	0.981989979743958
2019	0.979560017585754
2020	0.983640015125275