Year	gross (GPI)
1973	0.663900017738342
1977	0.467779994010925
1978	0.404500007629395
1979	0.385159999132156
1980	0.375360012054443
1981	0.376579999923706
1982	0.39699000120163
1983	0.435920000076294
1985	0.453689992427826
1986	0.486510008573532
1987	0.4894799888134
1990	0.567820012569427
1991	0.56165999174118
1992	0.598129987716675
1993	0.607999980449677
1994	0.590309977531433
1995	0.605660021305084
1999	0.606549978256226
2000	0.608539998531342
2001	0.622290015220642
2002	0.646889984607697
2004	0.691359996795654
2005	0.683910012245178
2006	0.708589971065521
2007	0.718869984149933
2008	0.737150013446808
2009	0.774699985980988
2010	0.804040014743805
2011	0.852100014686584
2012	0.877399981021881
2013	0.889240026473999
2014	0.894890010356903
2015	0.907100021839142
2016	0.938477694988251
2017	0.894429981708527
2018	0.97542804479599
2019	0.973486602306366
2020	0.929619491100311