Year	% net
1971	70.19831
1972	70.58994
1973	71.20154
1974	76.53078
1975	76.47202
1976	77.38921
1977	76.91629
1978	76.13394
1979	75.53121
1981	76.80322
1982	77.59085
1983	78.83851
1984	78.90733
1986	80.26647
1987	80.10621
1990	78.43803
1991	80.9996
1992	83.63754
1993	92.06388
1994	93.9031
1995	94.8189
1996	93.93028
1997	92.76342
1998	93.50332
1999	94.65621
2000	94.68536
2001	94.95354
2002	95.64137
2003	95.47093
2004	95.02938
2005	95.55691
2006	92.34619
2007	91.17435
2008	92.61934
2009	94.46231
2010	96.16818
2011	92.958
2012	90.8005
2013	93.84317
2014	97.18701
2015	98.13521
2017	97.13247