Year	% net
1970	74.30772
1971	82.43436
1972	85.01582
1973	87.09446
1975	88.80241
1976	88.47768
1978	90.59886
1979	89.17121
1980	88.11547
1981	86.77832
1982	85.80853
1983	84.67357
1984	84.44922
1985	85.02362
1986	84.99681
1987	85.78162
1988	84.95178
1989	86.41496
1990	86.60642
1999	93.12762
2000	94.87504
2001	96.15982
2002	98.30693
2004	98.0224
2005	97.56968
2006	98.188
2007	98.00928
2008	97.00675
2009	94.08748
2010	95.62248
2011	94.53537
2012	93.93236
2013	93.05661
2014	90.58017
2015	87.28892
2017	86.23979