Year	% net
1970	61.56958
1971	61.15264
1972	62.62828
1973	66.52705
1974	67.76785
1975	69.6831
1976	70.26208
1977	69.79004
1978	67.49787
1979	67.69207
1980	68.95219
1981	70.4088
1982	71.17481
1983	71.82961
1984	72.66457
1985	74.21377
1986	75.81065
1987	76.5423
1988	77.57353
1989	78.91102
1990	78.74079
1991	79.3105
1992	79.41995
1993	79.98485
1994	80.27676
1995	79.68949
1996	79.65362
1997	79.71624
1998	80.5623
1999	81.95255
2000	82.7559
2001	82.95781
2002	83.03127
2003	85.43066
2004	86.59522
2005	87.17036
2006	87.43211
2007	88.65234
2008	88.76001
2009	89.02329
2010	89.19184
2011	89.1941
2012	89.19124
2013	89.16761
2014	89.22499
2015	89.08243
2016	89.26459
2017	89.1338
2018	89.23946