Year	% net
1970	45.43222
1971	45.36313
1972	48.42713
1973	50.22316
1974	51.27015
1975	54.91671
1976	57.61344
1977	59.61008
1978	61.26005
1979	60.16032
1980	63.55922
1981	63.20387
1982	65.14146
1983	66.31042
1984	67.94353
1985	68.88569
1986	70.35863
1987	71.75648
1988	73.14971
1989	73.47468
1990	75.62916
1991	76.90545
1992	73.96775
1993	74.68079
1994	77.12459
1995	75.6631
1996	78.46364
1997	78.40979
1999	78.79581
2000	79.91817
2001	82.13621
2002	84.38244
2003	85.07841
2004	85.99539
2005	85.82253
2006	85.99398
2007	87.76272
2008	88.59492
2009	89.32003
2010	90.90097
2011	91.32452
2012	92.68248
2013	92.03454
2014	91.52865
2015	91.49824
2016	91.61148
2017	91.80524
2018	92.14038