Year	% net
1972	93.48455
1973	93.16292
1974	93.18122
1975	93.26381
1976	93.5232
1977	93.56574
1978	93.68311
1979	93.84476
1980	93.77575
1981	93.18765
1982	93.20815
1983	92.96757
1984	93.57571
1985	93.59326
1986	94.16172
1987	94.5669
1988	95.06255
1989	94.89677
1990	94.99092
1991	95.32478
1992	95.09255
1993	94.83711
1994	94.72666
1995	94.26659
1996	94.62246
1997	94.5234
1998	95.12226
1999	95.0083
2000	94.6293
2001	95.00901
2002	95.32602
2003	96.03353
2004	95.47854
2005	95.05319
2006	95.0962
2007	95.12766
2008	95.39694
2009	95.12563
2010	95.42895
2011	95.61241
2012	95.5845
2013	95.94929
2014	95.68722
2015	95.85257
2016	95.88099
2017	94.97764
2018	94.87481