Year	gross (GPI)
1972	1.1828099489212
1973	1.12011003494263
1974	1.10923004150391
1975	1.14652001857758
1976	1.21931004524231
1977	1.05560994148254
1980	1.07475996017456
1981	0.957040011882782
1999	0.92562997341156
2000	0.957970023155212
2001	0.937990009784698
2002	1.02591001987457
2004	1.05342996120453
2005	0.932009994983673
2006	0.981649994850159
2007	0.997439980506897
2008	1.09983003139496
2011	0.967019975185394
2012	0.988200008869171
2013	1.01935005187988
2018	1.01494002342224