Year	% net
1970	56.41824
1971	56.45895
1972	57.74514
1973	58.78744
1974	59.451
1975	60.72492
1976	62.24588
1977	63.05442
1978	63.68734
1979	65.26127
1980	66.37092
1981	66.75488
1982	67.20985
1983	67.87008
1984	69.11031
1985	69.69341
1986	70.62051
1987	71.71951
1988	72.47846
1989	72.56397
1990	72.90577
1991	73.526
1992	70.94073
1993	71.39096
1994	73.57916
1995	72.74886
1996	74.83709
1997	75.26223
1999	76.02722
2000	76.68457
2001	77.92055
2002	78.95745
2003	79.40602
2004	79.93857
2005	80.2983
2006	80.5827
2007	81.78496
2008	82.67346
2009	82.90693
2010	84.13909
2011	83.87165
2012	84.52109
2013	83.3921
2014	83.23739
2015	83.24524
2016	83.5107
2017	83.76548
2018	84.05164