Year	% net
1974	48.13205
1975	53.19573
1976	55.06298
1977	56.11652
1978	57.47948
1979	58.65683
1980	61.10869
1981	59.04008
1982	58.87349
1983	59.37407
1984	59.12758
1985	60.50765
1986	60.81042
1987	61.81253
1988	63.3931
1989	62.83298
1990	63.89757
1991	65.18306
1992	65.29212
1993	64.35303
1994	66.1665
1995	67.83185
1996	69.49139
1997	71.1024
1998	72.07722
1999	73.46059
2000	73.15722
2001	74.00953
2002	74.25208
2003	73.79626
2004	75.81996
2005	75.16683
2006	75.11725
2007	75.36628
2008	75.40196
2009	75.13246
2010	74.6868
2011	74.97573
2012	73.82884
2013	73.13051
2014	73.56486
2015	72.70735
2016	73.75093
2017	73.90341
2018	74.27317