Year	% net
1975	73.38142
1976	74.14046
1977	75.10009
1978	75.56159
1979	75.99452
1980	76.61292
1981	76.99051
1982	77.46085
1983	77.89215
1984	78.14864
1985	78.78205
1986	79.93555
1987	80.53791
1988	80.73092
1989	81.03931
1990	81.18913
1991	81.41288
1992	82.12079
1993	85.1068
1994	87.10998
1995	87.25775
1996	87.63187
1997	87.50363
1998	86.32926
1999	86.50022
2000	87.16646
2001	87.80873
2002	88.69977
2003	89.06678
2004	89.4852
2005	90.59826
2006	90.58935
2007	90.2333
2008	90.918
2009	91.09391
2010	91.46895
2011	90.66274
2012	90.25664
2013	90.53868
2014	90.84754
2015	91.19895
2016	91.32184
2017	91.44627
2018	91.46641