Year	% net
1970	88.19249
1971	88.20691
1972	88.43388
1973	89.0743
1974	89.10555
1975	89.21794
1976	89.85828
1977	90.48672
1978	90.7176
1979	91.51539
1980	93.76925
1981	93.96744
1982	94.69893
1983	94.36043
1984	94.36957
1985	94.36554
1986	95.10977
1987	95.86127
1988	96.32005
1989	96.31686
1990	96.64282
1991	96.59177
1992	96.31826
1993	95.95763
1994	95.61696
1995	95.74211
1996	95.59977
1997	95.1444
1999	96.20673
2001	96.34288
2002	95.91884
2003	96.1567
2004	95.92179
2005	96.19609
2006	96.4647
2007	96.74235
2008	96.86179
2009	96.30548
2010	95.96256
2011	95.73723
2012	95.67427
2013	95.69497
2014	95.74027
2015	95.96038
2016	96.21472
2017	95.64335
2018	95.5958