Year	% net
1970	45.03254
1971	44.98474
1972	48.23895
1973	50.16283
1974	51.3046
1975	55.26824
1976	58.20445
1977	60.35605
1978	62.15157
1979	60.98664
1980	64.63843
1981	64.1923
1982	66.24081
1983	67.42744
1984	69.1034
1985	70.02914
1986	71.50024
1987	72.96083
1988	74.41315
1989	74.69012
1990	77.06453
1991	78.47111
1992	75.05173
1993	75.65074
1994	78.2029
1995	76.34601
1996	79.27031
1997	79.01756
1999	79.08428
2000	80.18579
2001	82.55528
2002	84.94683
2003	85.60437
2004	86.52999
2005	86.15037
2006	86.11738
2007	87.87633
2008	88.52613
2009	89.07465
2010	90.29378
2011	90.72715
2013	91.35238
2014	90.67917
2015	90.59505
2016	90.73243
2017	91.07688
2018	91.48722