Year	% net
1972	88.70877
1973	89.09852
1974	88.98993
1975	89.33191
1976	90.03938
1977	90.58422
1978	90.95081
1979	91.19743
1980	93.45673
1981	93.3251
1982	93.83304
1983	93.32893
1984	92.83787
1985	92.84032
1986	93.6429
1987	94.69295
1988	95.37129
1989	95.80302
1990	95.64982
1991	95.87288
1992	95.36865
1993	95.26907
1994	95.18406
1995	95.55578
1996	95.51288
1997	95.62598
1998	96.00994
1999	95.78852
2000	95.83669
2001	96.17377
2002	95.77285
2003	95.96411
2005	95.89875
2006	96.18054
2007	96.34957
2009	96.25117
2010	95.54446
2011	95.6082
2012	95.48131
2013	95.554
2014	95.70475
2015	96.19104
2016	96.40149
2017	96.23576