Year	% net
1971	91.89007
1972	92.33958
1973	93.45366
1974	95.04823
1975	95.40773
1976	95.60764
1977	95.05127
1978	94.34745
1979	93.37635
1980	91.72432
1981	93.2125
1982	93.42299
1983	94.2614
1984	94.1936
1985	94.07422
1986	93.17156
1987	90.95459
1988	91.72147
1989	91.19082
1990	90.8961
1991	90.62979
1992	88.94075
1993	87.30481
1994	86.98576
1995	88.64463
1996	88.44979
1997	89.63678
1998	93.39902
1999	94.60154
2000	95.38317
2001	94.30742
2002	95.15271
2003	95.74776
2004	96.728
2005	95.79944
2006	95.50275
2007	95.31785
2010	96.8096
2011	96.95325
2012	97.73128
2013	97.49025
2014	96.53303
2015	97.32526
2016	97.94221
2017	98.22037