Year	% net
1971	97.7837
1972	97.02108
1973	97.22484
1974	96.06486
1975	95.8424
1976	95.95459
1977	95.94391
1978	95.83157
1979	95.02001
1980	93.77915
1981	91.9501
1982	89.98083
1983	88.43755
1986	87.04801
1987	87.66118
1988	88.55462
1989	89.00253
1990	89.36873
1991	88.84745
1992	87.95219
1993	87.58849
1994	87.64264
1995	87.94268
1996	88.80624
1998	94.67116
1999	94.72039
2000	94.79352
2001	94.63713
2002	94.80837
2003	94.8888
2004	94.91075
2005	94.81635
2006	95.19238
2007	95.33288
2008	95.40736
2009	95.46813
2010	95.20748
2011	97.52724
2012	95.33033
2013	95.2089
2014	95.35688
2015	95.75035
2016	95.87164
2017	95.78041