Year	% net
1970	70.63176
1971	70.55512
1972	71.77007
1973	74.56648
1974	75.55734
1975	76.8612
1976	77.47095
1977	77.332
1978	75.90416
1979	76.2828
1980	77.18082
1981	78.23412
1982	78.88836
1983	79.33452
1984	79.84848
1985	80.7924
1986	81.75892
1987	82.21874
1988	83.07168
1989	84.06308
1990	83.86539
1991	84.19833
1992	84.17269
1993	84.37746
1994	84.34765
1995	83.6134
1996	83.29134
1997	83.12236
1998	83.78033
1999	84.82678
2000	85.42558
2001	85.54186
2002	85.44146
2003	86.7533
2004	87.78467
2005	88.22677
2006	88.35748
2007	89.66666
2008	89.47805
2009	89.45262
2010	89.57565
2011	89.41354
2012	89.69267
2013	89.65646
2014	89.9072
2015	89.88489
2016	90.1506
2017	90.02743
2018	90.26697