Year	% net
1971	93.21163
1972	94.54709
1973	95.47561
1975	99.46797
1976	99.90722
1977	99.15999
1978	98.59984
1979	98.68616
1980	99.15964
1981	99.18396
1983	99.58957
1984	99.75934
1985	99.79266
1986	99.8015
1987	99.20641
1988	98.60385
1989	99.23004
1990	99.22275
1991	99.66298
1992	99.65
1993	99.98866
1994	99.98101
1995	99.95766
1996	99.94339
1997	99.93531
1999	99.85712
2000	99.81425
2001	99.76442
2002	99.82002
2003	99.85653
2004	99.73118
2005	99.65855
2006	99.71458
2007	99.82284
2008	99.82827
2009	99.77222
2010	99.71354
2011	99.73417
2012	99.69626
2013	99.55937
2014	99.47472
2015	99.39278
2016	98.78967
2017	97.27171