Year	% net
1981	89.59942
1982	88.15434
1983	85.11353
1984	91.68477
1985	94.56526
1986	95.87482
1987	97.08417
1988	99.55368
1990	99.20278
1994	99.14782
1998	99.82899
2000	99.05232
2001	97.28274
2002	95.91699
2003	95.57941
2004	94.56666
2005	95.31446
2006	96.31027
2007	96.65032
2008	96.15012
2009	95.43499
2010	94.47048
2011	93.2143
2012	93.65455
2013	93.09431
2014	93.20062
2015	93.24357
2016	92.59373
2017	92.86236
2018	93.42191