Year	gross (GPI)
1971	0.828930020332336
1972	0.835799992084503
1974	0.840590000152588
1988	0.923470020294189
1989	0.945949971675873
1990	0.955370008945465
2005	0.956520020961761
2006	0.958639979362488
2007	0.96356999874115
2008	0.963970005512238
2009	0.968010008335114
2011	0.971119999885559
2012	0.976050019264221
2014	0.989859998226166
2015	0.993740022182465
2016	0.996739983558655
2018	1.0093799829483
2019	1.01898002624512