Year	% net
1977	80.196
1979	80.37668
1980	80.75146
1982	81.21998
1983	82.09055
1985	84.09295
1986	84.38492
1987	84.41857
1988	84.37496
1989	84.83711
1990	85.46445
1992	90.54048
1993	91.53542
1994	95.87305
1995	96.47916
1996	96.01478
1997	95.23164
1999	90.94398
2000	90.68465
2001	90.39445
2002	90.07332
2003	89.86307
2004	89.70683
2005	93.47937
2006	93.37342
2007	93.42457
2008	93.45841
2009	93.52342
2010	93.4033
2011	93.70787
2012	93.94162
2013	94.0829
2014	93.69613
2015	94.36077
2016	94.68814
2017	95.32789