Year	% net
1970	49.67083
1971	49.63676
1972	50.3963
1973	52.31758
1974	51.8638
1975	52.6177
1976	54.13775
1977	54.82382
1978	55.08539
1979	56.52305
1980	58.33677
1981	60.01068
1982	59.48363
1983	60.69324
1984	61.14394
1985	60.87187
1986	61.40048
1987	60.58109
1988	60.70418
1989	59.76462
1990	57.86459
1991	60.99902
1992	60.50288
1993	60.6073
1994	61.32111
1995	62.11463
1996	60.82281
1997	59.84781
1998	58.71865
1999	57.41334
2005	66.47881
2006	68.22294
2007	69.4833
2008	72.21403
2015	76.17704
2016	76.42514
2017	76.56647
2018	77.02801