Year	% net
1977	75.95415
1978	76.45086
1981	77.33552
1982	77.28593
1983	76.90481
1984	76.37395
1985	76.31341
1986	76.72948
1987	77.92634
1988	79.7278
1989	81.80276
1990	83.53766
1991	84.35829
1992	84.41117
1993	83.62288
1994	82.74739
1995	89.20925
1996	91.15135
1999	95.72929
2000	95.57305
2001	95.28922
2002	95.16827
2003	94.93663
2004	94.779
2005	93.7217
2006	93.28557
2007	93.25728
2008	93.90496
2009	94.03709
2010	93.96341
2011	93.86312
2012	93.70195
2013	93.6342
2014	93.77291
2015	93.31881
2016	93.53763
2017	93.19583