Year	% net
1970	43.11841
1971	42.00246
1972	43.62683
1973	47.94461
1974	47.08739
1975	48.56381
1976	48.74681
1977	51.56904
1978	48.59345
1979	48.70773
1980	50.10498
1981	51.8604
1982	51.75391
1983	53.59592
1984	55.57914
1985	55.54113
1986	57.58521
1987	55.60573
1988	58.64308
1989	61.88953
1990	61.96852
1991	62.18648
1992	62.96162
1993	64.94941
1994	66.56263
1995	66.7875
1996	67.00292
1997	66.99763
1998	65.99324
1999	66.86044
2000	68.88753
2001	69.21381
2002	70.51603
2003	78.03525
2004	80.53169
2005	82.34337
2006	83.82396
2007	85.65859
2008	86.17493
2009	86.91173
2010	87.00896
2011	86.37355
2012	86.67464
2013	86.87741
2014	87.21258
2015	86.75207
2016	86.98376
2017	86.9749
2018	86.84744