Year	% net
1970	41.74279
1971	41.39987
1972	44.1107
1973	47.17647
1974	47.03542
1975	49.1171
1976	50.86421
1977	51.8217
1978	52.84428
1979	53.67104
1980	54.9314
1981	55.79434
1982	55.30024
1983	55.6955
1984	55.44057
1985	55.00724
1986	54.94009
1987	54.5829
1988	56.4482
1989	56.13793
1990	55.3683
1991	56.69984
1992	56.61936
1993	56.51054
1994	57.26982
1995	58.34656
1996	58.54181
1997	60.30086
1998	60.30411
1999	59.98559
2000	62.09739
2001	63.92301
2002	66.85468
2003	69.16743
2004	71.33412
2005	73.57192
2006	75.4721
2007	76.87688
2008	79.14792
2009	79.27102
2010	79.01711
2011	80.15009
2012	80.76015
2014	81.59401
2015	81.39644
2016	81.49674
2017	81.42673
2018	81.34393