Year	% net
1977	96.42127
1979	97.91599
1980	98.44774
1981	97.5045
1982	97.38166
1983	94.71105
1984	94.13783
1985	93.78456
1986	95.13323
1987	96.7241
1988	98.04386
1991	97.92838
1992	96.34972
1993	97.97415
1994	97.27382
1995	97.21866
1996	97.66343
2000	99.02054
2002	98.75985
2003	97.74291
2004	96.32343
2005	95.94271
2006	96.15016
2007	97.18781
2008	97.77193
2009	97.64271
2010	97.45188
2011	97.57639
2012	97.81485
2013	97.82413
2014	97.63696
2015	98.01233
2016	98.24648
2017	98.87476