Year	% net
1970	44.66827
1971	44.61006
1972	45.90615
1973	47.05359
1974	47.55197
1975	49.33274
1976	50.87216
1977	51.94379
1978	52.87928
1979	55.2264
1980	56.78126
1981	57.52132
1982	58.28564
1983	59.25484
1984	60.59346
1985	61.37404
1986	62.64116
1987	64.07296
1988	65.22261
1989	65.35466
1990	66.16068
1991	67.12508
1992	63.49232
1993	64.21807
1994	67.38675
1995	66.00638
1996	69.13606
1997	69.51657
1999	71.25089
2000	72.17208
2001	73.59948
2002	74.82221
2003	75.51832
2004	76.23106
2005	76.7082
2006	77.17461
2007	78.62129
2008	79.69968
2009	79.89748
2010	81.34995
2011	81.39816
2013	81.617
2014	81.5384
2016	81.91049
2017	81.75467
2018	82.10073