Year	% net
1976	48.42576
1980	70.31534
1981	69.10873
1982	64.27174
1983	63.08491
1984	59.91207
1985	57.07667
1986	55.78313
1987	54.35093
1988	52.73154
1989	52.67746
1990	52.04343
1991	51.36883
1992	51.46872
1993	50.6785
1994	49.44943
1995	49.3284
1996	49.47382
1997	49.9158
1998	49.41601
1999	49.88716
2000	53.53133
2001	58.12348
2002	73.08069
2003	81.60833
2004	86.14656
2005	90.85074
2006	96.73047
2008	98.85617
2010	92.19632
2012	87.50078
2013	83.95066
2014	83.32041
2016	83.50466
2017	83.58042
2018	81.32921