Year	% net
1978	81.52149
1979	83.72982
1981	85.48519
1982	86.28121
1984	87.25526
1985	87.74356
1986	87.72016
1987	86.7118
1988	86.21487
1989	86.61881
1990	88.40258
1991	88.39777
1992	89.15286
1993	90.80926
1997	96.79393
1998	96.54876
1999	95.65375
2000	95.21821
2001	94.81912
2002	94.69751
2003	95.55174
2004	96.637
2005	97.21807
2006	97.61611
2007	97.79597
2008	96.84956
2009	95.93941
2010	95.43126
2011	95.08988
2012	95.16759
2013	95.19423
2014	95.57377
2015	95.91824
2016	96.14233
2017	95.62558