Year	% net
1970	66.45766
1971	66.24722
1972	67.28671
1973	71.06325
1974	72.41028
1975	74.25359
1976	74.77936
1977	73.78587
1978	70.98408
1979	70.73641
1980	71.84375
1981	73.09242
1982	73.71151
1983	74.51594
1984	75.50982
1985	77.60719
1986	79.97296
1987	81.03988
1988	82.02613
1989	83.72324
1990	83.54602
1991	84.03041
1992	83.89713
1993	84.37758
1994	84.66231
1995	84.0768
1996	84.28642
1997	83.98038
1998	84.94679
1999	86.51708
2000	87.13214
2001	87.37723
2002	87.52658
2003	90.15011
2004	91.04048
2005	91.47789
2006	91.86878
2007	92.99068
2008	93.58286
2009	93.77277
2010	93.93265
2011	93.8305
2012	93.82379
2013	93.83282
2014	93.79607
2015	93.91141
2016	93.94197
2017	93.99825
2018	93.9923