Year	% net
1970	71.67935
1971	71.57806
1972	72.43951
1973	74.63163
1974	75.33089
1975	76.42605
1976	77.05546
1977	77.09193
1978	76.06698
1979	76.38643
1980	77.49952
1981	78.33426
1982	78.77231
1983	79.02271
1984	79.26589
1985	79.89322
1986	80.66337
1987	80.97392
1988	81.63435
1989	82.31129
1990	81.97659
1991	82.27477
1992	82.04808
1993	82.09867
1994	82.0904
1995	81.72236
1996	81.44546
1997	81.48041
1998	82.04955
1999	82.74345
2000	83.36606
2001	83.60714
2002	83.82844
2003	85.13168
2004	86.16491
2005	86.78988
2006	87.21038
2007	88.44145
2008	88.65773
2009	88.62895
2010	88.63339
2011	88.65391
2012	89.00668
2013	88.99782
2014	89.22588
2015	89.16969
2016	89.41678
2017	89.26194
2018	89.4124