Year	gross (GPI)
1970	0.57134997844696
1974	0.566900014877319
1975	0.590449988842011
1976	0.591350018978119
1977	0.613600015640259
1984	0.773810029029846
1986	0.788879990577698
1987	0.790030002593994
1988	0.794139981269836
1989	0.799149990081787
1990	0.811689972877502
1991	0.820200026035309
1992	0.820909976959229
1993	0.835569977760315
1994	0.833970010280609
1995	0.844919979572296
1998	0.836749970912933
2012	0.851029992103577
2018	0.894339978694916