Year	% net
1970	26.01926
1971	26.16402
1972	28.10352
1973	30.29236
1974	31.36137
1975	33.65436
1976	35.94008
1977	38.34066
1978	40.47079
1979	41.85801
1980	42.69225
1981	43.0309
1982	44.2543
1983	44.96218
1984	45.79015
1985	46.78026
1986	48.72813
1987	49.98278
1988	50.45219
1989	51.38951
1990	54.1539
1991	54.39976
1992	53.86783
1993	55.08868
1994	57.50145
1995	57.84712
1996	58.18218
1997	59.59376
1998	61.2692
1999	62.94523
2000	64.12661
2001	64.97429
2002	65.67071
2003	66.62368
2004	68.03607
2005	67.73298
2006	67.78167
2007	67.041
2008	68.45695
2009	70.35118
2010	69.8294
2011	71.85477
2012	71.63868
2013	69.54146
2014	70.24372
2015	71.01426
2016	72.02356
2017	72.39826
2018	72.79815