Year	gross (GPI)
1971	0.457830011844635
1972	0.556599974632263
1973	0.457249999046326
1974	0.454899996519089
1975	0.450340002775192
1976	0.501389980316162
1977	0.520529985427856
1978	0.508279979228973
1979	0.522719979286194
1981	0.495469987392426
1982	0.486420005559921
1983	0.476870000362396
1984	0.473360002040863
1985	0.454650014638901
1986	0.460119992494583
1987	0.440679997205734
1988	0.445520013570786
1989	0.442950010299683
1990	0.447019994258881
1991	0.459780007600784
1992	0.460409998893738
1993	0.465629994869232
1994	0.487329989671707
1995	0.506510019302368
1996	0.526130020618439
1997	0.563780009746552
1998	0.589070022106171
1999	0.620119988918304
2000	0.668340027332306
2001	0.704800009727478
2002	0.728890001773834
2003	0.754700005054474
2004	0.776059985160828
2005	0.801479995250702
2006	0.826610028743744
2007	0.840040028095245
2008	0.837170004844666
2009	0.840550005435944
2010	0.823279976844788
2011	0.851849973201752
2012	0.842149972915649
2013	0.842970013618469
2014	0.846140027046204
2015	0.813708543777466
2016	0.819310009479523
2017	0.836079776287079
2018	0.843308448791504
2019	0.838948607444763
2020	0.848070025444031