Year	% net
1971	92.7428
1972	92.10748
1973	91.52476
1974	90.77491
1975	90.61832
1976	91.53545
1977	91.88208
1978	92.35679
1979	92.91357
1980	93.01502
1981	92.43034
1982	90.40533
1983	88.4294
1984	87.10393
1985	86.56236
1986	92.05286
1987	93.89636
1988	95.44371
1989	95.9975
1990	95.82034
1991	95.1169
1992	94.15866
1993	93.53313
1994	98.9616
1995	99.2071
1996	99.38737
1997	99.66541
1999	99.35646
2000	99.39074
2001	99.34888
2002	99.2999
2003	98.80214
2004	98.21145
2005	98.11317
2006	98.50395
2007	99.32514
2008	99.59125
2009	99.79754
2010	99.51312
2011	99.22106
2012	98.48654
2015	96.42447
2016	97.32553
2017	98.64765