Year	% net
1971	42.10101
1972	46.16797
1973	49.02851
1974	52.76906
1975	56.74901
1976	60.85402
1977	64.336
1978	67.1441
1979	70.23172
1980	73.52958
1981	76.72376
1984	82.95148
1985	84.12026
1986	85.92878
1989	84.82576
1991	89.17004
1992	87.53327
1996	95.96534
1997	94.43183
1998	93.92633
1999	93.35907
2000	92.31392
2001	92.21848
2002	92.02118
2003	92.80124
2004	93.43617
2005	94.18923
2006	93.85379
2007	93.96953
2008	93.31706
2009	94.77398
2010	95.07951
2011	95.84121
2012	96.54936
2013	97.91041
2014	98.237
2015	97.91916
2016	98.39339
2017	98.19101