Year	% net
1981	79.03838
1982	78.80167
1983	78.47525
1984	78.32774
1985	78.16349
1986	77.68906
1987	77.26125
1988	77.15978
1989	76.81958
1990	77.33685
1991	78.14829
1992	78.90112
1993	80.00502
1994	81.07155
1999	84.63215
2000	84.66111
2001	84.14402
2002	83.37213
2003	83.3568
2004	83.98112
2005	84.72205
2006	85.22291
2007	84.85637
2008	84.53242
2009	83.63971
2010	83.68751
2011	83.20701
2012	81.17079
2013	83.55855
2014	84.47933
2015	85.13441
2016	85.82816
2017	85.32946