Year	% net
1970	64.2273
1971	63.42214
1972	64.40947
1973	65.86528
1974	67.88289
1975	70.48361
1976	72.19924
1977	72.87719
1978	72.27324
1979	72.22837
1980	73.10382
1981	74.32241
1982	75.4705
1983	75.77355
1984	76.62084
1985	77.55389
1986	76.98368
1987	76.79307
1988	76.3469
1989	75.59069
1990	74.16419
1991	74.17889
1992	73.48413
1993	73.37246
1994	74.53945
1995	74.25186
1996	74.75559
1997	74.81691
1998	74.89126
1999	75.04155
2000	77.91264
2001	79.27656
2002	80.02923
2003	80.78428
2007	82.6164
2009	83.13772
2010	83.90797
2013	84.51111
2014	84.78411
2015	85.15858
2016	85.42333
2017	85.98525
2018	86.00632