Year	gross (GPI)
1981	1.02197003364563
1982	1.01301002502441
1983	0.995130002498627
1984	1.00894999504089
1985	1.01609003543854
1986	1.01294994354248
1987	0.995589971542358
1990	0.994329988956451
1991	0.982110023498535
1993	0.980449974536896
1994	0.99031001329422
1995	0.9896399974823
1996	0.987649977207184
1998	1.0255800485611
1999	1.02755999565125
2005	0.989250004291534
2013	0.991720020771027
2014	0.996640026569366
2015	0.999750018119812
2016	0.998329997062683
2017	0.99234002828598
2018	0.998839974403381
2019	1.00705003738403
2020	0.995100021362305