Year	gross (GPI)
1976	0.907710015773773
1978	0.904850006103516
1979	0.913110017776489
1980	0.891520023345947
1981	0.888339996337891
1982	0.90106999874115
1983	0.932120025157928
1984	0.929149985313416
1985	0.907209992408752
1986	0.904959976673126
1987	0.919340014457703
1988	0.924399971961975
1989	0.925499975681305
1990	0.914520025253296
1991	0.91923999786377
1992	1.01195001602173
1993	1.05314004421234
1994	1.0220400094986
1995	0.99397999048233
1996	0.997720003128052
1997	0.974699974060059
1999	0.962639987468719
2000	0.96644002199173
2001	0.973630011081696
2004	0.964119970798492
2005	0.965430021286011
2006	0.974629998207092
2007	0.992269992828369
2008	0.99889999628067
2009	1.03197002410889
2010	1.00547003746033
2011	0.991559982299805
2012	0.975859999656677
2013	0.95973002910614
2014	0.9444500207901
2015	0.956219971179962
2016	0.970860004425049
2017	0.989030003547668
2018	1.00539004802704
2019	1.01136004924774
2020	1.02103996276855
2021	1.03113996982574