Year	% net
1970	75.91729
1971	76.04317
1972	76.7716
1973	77.36504
1974	78.54901
1975	79.07815
1976	79.48093
1977	80.44322
1978	79.87942
1979	79.61516
1980	79.58678
1981	80.40362
1982	81.50966
1983	81.6808
1984	81.97794
1985	82.40675
1986	81.99366
1987	82.20508
1988	81.79236
1989	81.57716
1990	80.18686
1991	79.83135
1992	79.34718
1993	79.25071
1994	80.05484
1995	79.95181
1996	79.98533
1997	80.10424
1998	80.07822
1999	79.86637
2001	82.64908
2002	83.13594
2013	85.26705
2014	85.31314
2015	85.55724
2017	85.82278
2018	85.68541