Year	% net
1970	45.31479
1971	45.26503
1972	48.50764
1973	50.42056
1974	51.55677
1975	55.49205
1976	58.40663
1977	60.54161
1978	62.3224
1979	61.16491
1980	64.78789
1981	64.34431
1982	66.37685
1983	67.55419
1984	69.21739
1985	70.13592
1986	71.59565
1987	73.04499
1988	74.48601
1989	74.76029
1990	77.11923
1991	78.51462
1992	75.121
1993	75.7168
1994	78.25106
1995	76.41084
1996	79.32423
1997	79.09104
1999	79.17522
2000	80.26693
2001	82.59149
2002	84.95158
2003	85.58951
2004	86.47564
2005	86.07028
2006	86.04888
2007	87.7803
2008	88.46904
2009	89.02694
2010	90.24169
2011	90.68619
2013	91.37168
2014	90.71351
2015	90.63062
2016	90.77254
2017	91.12317
2018	91.52754