Year	% net
1971	76.33968
1972	79.20479
1973	80.26908
1974	81.86211
1975	85.28601
1976	82.12487
1977	82.11388
1978	80.05571
1979	80.69142
1980	82.3983
1981	81.99603
1982	80.6088
1983	83.25855
1984	86.6106
1985	91.05123
1986	96.14373
1987	95.51585
1988	98.27366
1989	99.0614
1991	99.4111
1992	97.01005
1993	98.02282
1994	97.93377
1995	99.114
1996	99.858
1997	99.60053
1998	96.968
1999	96.875
2000	95.77521
2001	93.01535
2002	93.09968
2003	92.38448
2004	91.59966
2005	89.10805
2006	90.50941
2011	90.22637
2012	91.19673
2013	92.26165
2014	94.30002
2015	96.45648
2016	96.26462
2017	97.27864
2018	96.71489