Year	% net
1981	86.79716
1982	86.43674
1983	86.04539
1984	83.91263
1985	82.96574
1986	82.27431
1987	82.68106
1988	83.68279
1989	85.279
1990	86.03502
1991	85.9071
1992	85.65691
1993	85.2513
1994	85.77435
1995	85.38573
1996	86.15553
1998	86.72637
2000	87.65268
2001	88.393
2002	89.63972
2003	92.17944
2004	89.73208
2005	90.21064
2006	87.89837
2007	87.78942
2008	87.79026
2009	88.4559
2010	88.95108
2011	89.94443
2012	88.99758
2013	88.62825
2014	87.737
2015	87.62704
2016	88.16314
2017	89.6541