Year	% net
1978	80.05266
1979	80.47664
1981	81.58125
1982	81.91595
1984	83.44077
1985	84.15649
1986	84.35261
1987	83.65765
1988	82.9458
1989	83.42451
1990	86.16205
1991	86.89095
1992	88.49068
1993	90.48536
1997	96.34304
1998	95.78964
1999	94.91072
2000	94.31993
2001	93.9387
2002	93.66541
2003	94.67993
2004	95.61765
2005	96.31776
2006	96.73712
2007	97.15777
2008	96.51343
2009	95.54594
2010	95.17598
2011	94.66102
2012	93.81961
2013	94.82971
2014	95.13349
2015	95.03477
2016	95.27672
2017	95.59103