Year	gross (GPI)
1971	0.854659974575043
1972	0.87321001291275
1973	0.794690012931824
1974	0.785870015621185
1981	1.1425199508667
1984	0.887189984321594
1985	0.968190014362335
1989	1.3119900226593
1990	1.34238994121552
1992	1.20299994945526
1999	1.56147003173828
2000	1.62344002723694
2001	1.59027004241943
2007	1.52438998222351
2009	1.54024994373322
2010	1.53471004962921
2011	1.54765999317169