Year	% net
1970	82.63162
1971	82.9887
1972	83.54588
1973	84.35147
1974	84.94407
1975	85.04671
1976	85.78365
1977	86.78217
1978	87.3812
1979	89.09069
1980	89.57353
1981	90.80076
1982	90.98526
1983	90.97564
1984	90.82771
1985	91.29281
1986	91.00853
1987	91.0213
1988	90.6529
1989	89.83831
1990	90.31524
1991	90.6299
1992	91.37274
1993	91.67598
1994	91.09194
1995	90.98822
1996	91.4374
1997	90.45181
1999	93.56133
2000	94.19936
2002	94.26777
2003	93.64849
2004	93.96036
2005	94.16808
2006	93.95135
2007	93.68639
2008	95.09439
2009	94.86528
2010	94.91106
2011	94.795
2012	94.87661
2013	93.67422
2014	93.52485
2015	93.46321
2016	93.66489
2017	93.72012
2018	93.75228