Year	% net
1970	59.06959
1971	55.25332
1972	55.88081
1973	56.20799
1974	63.82574
1976	64.22977
1977	64.86645
1978	58.41162
1979	59.36104
1980	59.45404
1981	59.55338
1982	63.38954
1983	62.79703
1984	63.57605
1985	65.65393
1986	65.38437
1987	66.51564
1988	67.28966
1989	66.35433
1990	65.08796
1991	66.2798
1992	66.34746
1993	64.00362
1994	64.91882
1995	63.89581
1996	64.10472
1998	57.22832
1999	54.28467
2000	74.50071
2001	76.2845
2002	78.78223
2003	81.61161
2004	81.89118
2005	83.75431
2006	86.06502
2007	84.60323
2008	86.17053
2009	86.82353
2010	88.6368
2011	88.93112
2012	89.19998
2013	86.3829
2014	87.35942
2015	88.60833
2016	90.57671
2017	93.31062