Year	% net
1970	57.3733
1971	57.07084
1972	58.78515
1973	62.19406
1974	62.00952
1975	63.24436
1976	63.63554
1977	65.27442
1978	62.99938
1979	63.05389
1980	64.03115
1981	65.26194
1982	65.34128
1983	66.86557
1984	68.0134
1985	68.09781
1986	69.60095
1987	68.42734
1988	70.69364
1989	72.92956
1990	73.09375
1991	72.97635
1992	73.2278
1993	74.32126
1994	75.20958
1995	75.10909
1996	74.97807
1997	74.69865
1998	73.67256
1999	74.04166
2000	75.39169
2001	75.38968
2002	75.97041
2003	79.97745
2004	82.30155
2005	83.98378
2006	85.18058
2007	86.98178
2008	86.66069
2009	86.5986
2010	86.79966
2011	85.88894
2012	86.73428
2013	87.08056
2014	87.73493
2015	87.46799
2016	87.87303
2017	87.60735
2018	87.76227