Year	% net
1970	16.39486
1971	16.54676
1972	18.47699
1973	19.93757
1974	20.97082
1975	22.85345
1976	24.71331
1977	26.59398
1978	28.50828
1979	29.6427
1980	30.5353
1981	31.23244
1982	32.45844
1983	33.41935
1984	34.49951
1985	35.66422
1986	37.58226
1987	39.06077
1988	40.04394
1989	41.38714
1990	44.10312
1991	44.81082
1992	44.97919
1993	46.5842
1994	49.16294
1995	49.89786
1996	50.60875
1997	52.48074
1998	54.21987
1999	56.04599
2000	57.27447
2001	58.15786
2002	58.92159
2003	60.1101
2004	61.26398
2005	61.3243
2006	61.72198
2007	61.31596
2008	62.74357
2009	64.60698
2010	64.78242
2011	67.54172
2012	67.99245
2013	64.96358
2014	65.30866
2015	66.12616
2016	67.14597
2017	67.83487
2018	68.33189