Year	% net
1971	97.3487
1972	97.27084
1973	97.31155
1974	97.57172
1976	96.81501
1977	96.94516
1979	98.94168
1980	99.29482
1981	98.85366
1982	97.61584
1983	95.46911
1985	94.87775
1986	97.61482
1987	99.88708
1988	99.84556
1989	99.85966
1990	99.91749
1991	99.98827
1992	99.21937
1993	97.83304
1994	97.79167
1995	98.94106
1996	99.94659
1997	99.9391
1999	95.96275
2000	95.59312
2001	95.50102
2002	95.43218
2003	95.19437
2004	95.15357
2005	98.55515
2006	98.57178
2007	98.49684
2008	98.06303
2009	97.70589
2010	97.35002
2011	98.37009
2012	98.27769
2013	98.30237
2014	97.56809
2015	98.43569
2016	98.82171
2017	98.92727