Year	gross (GPI)
1975	0.651040017604828
1976	0.67833000421524
1977	0.685599982738495
1978	0.692409992218018
1979	0.709789991378784
1981	0.726189970970154
1982	0.723900020122528
1986	0.800069987773895
1990	0.775650024414063
1992	0.760469973087311
1994	0.8889399766922
1997	0.851599991321564
2004	0.952769994735718
2007	0.961059987545013
2010	0.971816539764404
2011	0.972994923591614
2012	0.975099623203278
2013	0.978912949562073
2014	0.983328223228455
2016	1.0017706155777
2017	1.00395524501801