Year	gross (GPI)
1971	0.436610013246536
1972	0.435570001602173
1973	0.473949998617172
1979	0.55952000617981
1980	0.572369992733002
1984	0.647019982337952
1988	0.675979971885681
2008	1.13591003417969
2012	1.23936998844147
2015	1.14092004299164
2018	1.12765002250671
2019	1.13996005058289
2020	1.19436001777649