Year	% net
1970	20.83903
1971	20.99864
1972	22.95944
1973	24.8019
1974	25.84945
1975	27.95398
1976	30.04804
1977	32.21966
1978	34.2844
1979	35.5662
1980	36.44057
1981	36.95937
1982	38.19878
1983	39.04165
1984	40.00418
1985	41.09111
1986	43.04586
1987	44.41625
1988	45.1372
1989	46.27774
1990	49.05288
1991	49.52334
1992	49.32367
1993	50.74294
1994	53.2611
1995	53.79957
1996	54.29436
1997	55.92108
1998	57.62595
1999	59.3733
2000	60.57024
2001	61.43204
2002	62.12412
2003	63.16248
2004	64.40082
2005	64.24293
2006	64.43329
2007	63.84027
2008	65.27432
2009	67.19797
2010	67.03865
2011	69.50265
2012	69.60627
2013	66.99178
2014	67.51367
2015	68.29196
2016	69.29603
2017	69.79347
2018	70.25002