Year	gross (GPI)
1971	1.02354001998901
1972	1.02113997936249
1973	1.01996004581451
1974	1.01884996891022
1975	1.01637005805969
1976	1.01276004314423
1977	1.00941002368927
1978	1.01135003566742
1979	1.01270997524261
1980	1.0116800069809
1983	1.0331699848175
1984	0.99974000453949
1985	0.993390023708344
1986	0.994780004024506
1987	0.995450019836426
1988	0.997699975967407
1989	1.00051999092102
1991	0.989409983158112
1992	0.98183000087738
1993	0.978500008583069
1996	0.986720025539398
1997	0.97969001531601
1999	0.983089983463287
2000	0.983439981937408
2001	0.982729971408844
2002	0.98131000995636
2003	0.980359971523285
2004	0.979730010032654
2005	0.981199979782104
2006	0.977609992027283
2007	0.974629998207092
2008	0.974510014057159
2009	0.974039971828461
2010	0.972440004348755
2011	0.975350022315979
2012	0.98063999414444
2013	0.986890017986298
2014	0.9825199842453
2015	0.977729976177216
2016	0.976989984512329
2017	0.97707998752594