Year	% net
1978	80.76859
1979	82.06106
1981	83.48026
1982	84.03964
1984	85.29788
1985	85.90369
1986	85.99373
1987	85.14763
1988	84.54219
1989	84.9854
1990	87.25722
1991	87.62745
1992	88.81443
1993	90.64369
1997	96.56315
1998	96.16022
1999	95.27329
2000	94.75798
2001	94.36783
2002	94.16888
2003	95.10527
2004	96.11468
2005	96.75623
2006	97.16459
2007	97.46832
2008	96.67695
2009	95.73719
2010	95.29992
2011	94.86901
2012	94.47334
2013	95.00651
2014	95.34711
2015	95.4637
2016	95.6976
2017	95.60786