Year	% net
1970	62.93308
1971	62.86506
1972	64.424
1973	66.66471
1974	66.67603
1975	67.96785
1976	68.91429
1977	70.3651
1978	69.75898
1979	70.24059
1980	71.43345
1981	72.78711
1982	74.13298
1983	75.12195
1984	75.90303
1985	76.15585
1986	76.90787
1987	76.66216
1988	77.8461
1989	79.36741
1990	78.76792
1991	79.21938
1992	79.35179
1993	79.72105
1994	80.26206
1995	79.86884
1996	80.22268
1997	79.88409
1998	79.65084
1999	79.83443
2000	80.83325
2001	81.33135
2002	81.58315
2003	83.54464
2004	84.79366
2005	86.02361
2006	87.00884
2007	88.65918
2008	88.78369
2009	88.94847
2010	89.24961
2011	89.03658
2012	89.58673
2013	89.85962
2014	90.13126
2015	90.12215
2016	90.42552
2017	90.26593
2018	90.30715