Year	% net
1970	25.58817
1971	25.74061
1972	27.70707
1973	29.90997
1974	30.97847
1975	33.28646
1976	35.59081
1977	38.01402
1978	40.17671
1979	41.57914
1980	42.42313
1981	42.7662
1982	44.00443
1983	44.7209
1984	45.55885
1985	46.56092
1986	48.53231
1987	49.80058
1988	50.27487
1989	51.22066
1990	54.02082
1991	54.26771
1992	53.72876
1993	54.9649
1994	57.40807
1995	57.75758
1996	58.06884
1997	59.46876
1998	61.14284
1999	62.81669
2000	64.00232
2001	64.85903
2002	65.51175
2003	66.4308
2004	67.79933
2005	67.46749
2006	67.49682
2007	66.74303
2008	68.17905
2009	70.12022
2010	69.6225
2011	71.7405
2012	71.50486
2013	69.35994
2014	70.06531
2015	70.81903
2016	71.82158
2017	72.1625
2018	72.57012