Year	% net
1970	75.20324
1971	75.34783
1972	76.16572
1973	76.84299
1974	78.09734
1975	79.0863
1976	79.65622
1977	80.53968
1978	80.00275
1979	79.69017
1980	79.7305
1981	80.52348
1982	81.33146
1983	81.5847
1984	82.00406
1985	82.38
1986	81.84792
1987	81.89234
1988	81.49063
1989	81.26788
1990	79.94867
1991	79.49605
1992	78.76807
1993	78.60027
1994	79.45769
1995	79.25936
1996	79.32864
1997	79.54958
1998	79.57752
1999	79.40929
2001	82.37982
2002	82.90284
2013	85.74335
2014	85.85604
2015	86.14665
2017	86.2564
2018	86.14369