Year	gross (GPI)
1971	0.378190010786057
1972	0.393240004777908
1973	0.409610003232956
1974	0.425830006599426
1975	0.434890002012253
1976	0.451139986515045
1977	0.454180002212524
1978	0.461430013179779
1984	0.479570001363754
1985	0.479499995708466
1988	0.513029992580414
1989	0.506070017814636
1990	0.526489973068237
1991	0.576669991016388
2001	0.722890019416809
2011	0.751640021800995
2012	0.85971999168396
2013	0.874719977378845
2015	0.878440022468567
2016	0.924759984016418
2017	0.965510010719299