Year	% net
1970	25.63522
1971	25.75968
1972	25.8865
1973	27.55121
1974	28.04596
1975	29.52034
1976	31.18855
1977	33.32262
1978	35.40057
1979	36.97815
1980	38.09185
1981	38.35971
1982	39.87887
1983	40.93627
1984	42.11484
1985	43.49402
1986	45.30352
1987	46.2808
1988	46.51207
1989	46.99447
1990	49.53894
1991	49.49954
1992	48.18395
1993	48.57591
1994	50.28378
1995	50.15599
1996	50.05013
1997	51.05404
1998	52.41088
1999	53.84579
2000	55.15492
2001	56.46022
2002	57.20318
2003	58.72127
2004	60.58895
2005	60.45304
2006	60.13836
2007	59.7538
2008	60.77392
2009	62.83868
2010	62.80266
2011	64.0549
2012	63.93499
2013	62.88557
2014	63.70357
2015	64.23228
2016	64.72554
2017	65.21272
2018	65.6165