Year	% net
1971	70.79908
1972	71.03988
1973	71.5326
1974	76.69045
1975	76.48503
1976	77.95317
1977	77.50675
1978	76.73477
1979	76.17908
1981	78.19176
1982	79.06131
1983	80.14477
1984	80.1808
1986	81.69551
1987	81.16813
1990	79.56314
1991	82.24123
1992	84.87946
1993	92.11067
1994	93.86034
1995	94.87488
1996	94.21612
1997	93.1328
1998	93.97631
1999	95.18473
2000	95.39748
2001	95.67337
2002	96.61247
2003	97.0797
2004	96.61894
2005	97.42833
2006	94.19442
2007	92.71672
2008	93.75392
2009	95.36203
2010	96.79978
2011	93.37553
2012	90.85161
2013	94.1207
2014	97.54052
2015	98.45768
2017	97.23472