Year	% net
1970	82.09352
1971	82.42277
1972	82.98216
1973	83.77803
1974	84.38711
1975	84.50609
1976	85.23868
1977	86.23791
1978	86.82977
1979	88.5547
1980	89.07445
1981	90.40533
1982	90.62152
1983	90.67659
1984	90.4924
1985	91.00355
1986	90.70569
1987	90.79437
1988	90.48351
1989	89.69951
1990	90.25333
1991	90.61181
1992	91.22504
1993	91.5072
1994	90.92953
1995	90.79513
1996	91.17746
1997	90.33224
1999	93.2279
2000	93.88268
2002	93.78135
2003	92.93204
2004	93.44467
2005	94.44212
2006	94.26767
2007	94.01144
2008	94.9695
2009	94.98723
2010	94.9795
2011	94.7871
2012	95.02038
2013	93.77863
2014	93.6813
2015	93.65848
2016	93.98719
2017	93.93952
2018	93.90213