Year	% net
1970	83.17324
1971	83.53382
1972	84.0524
1973	84.86603
1974	85.45782
1975	85.63768
1976	86.37492
1977	87.31722
1978	87.88024
1979	89.46254
1980	89.87694
1981	90.94067
1982	91.03863
1983	91.02334
1984	90.83735
1985	91.2501
1986	90.98568
1987	91.02937
1988	90.6685
1989	89.87707
1990	90.33373
1991	90.63183
1992	91.39047
1993	91.70207
1994	91.17576
1995	91.07574
1996	91.55162
1997	90.59165
1999	93.60942
2000	94.22767
2001	94.46592
2002	94.29361
2003	93.67196
2004	93.97811
2005	94.17077
2006	93.94626
2007	93.69869
2008	95.07321
2009	94.8686
2010	94.9263
2011	94.77554
2012	94.84527
2013	93.66306
2014	93.47957
2015	93.4024
2016	93.58351
2017	93.65373
2018	93.71661