Year	% net
1977	96.29779
1979	97.62043
1980	98.15498
1981	97.04024
1982	97.12267
1983	93.98158
1984	93.29294
1985	92.87257
1986	94.30415
1987	95.68513
1988	96.89028
1991	96.53405
1992	95.09398
1993	97.66637
1994	97.04167
1995	97.07828
1996	97.5397
1999	98.89581
2000	98.89887
2001	98.94338
2002	98.67874
2003	97.71071
2004	96.10918
2005	95.74554
2006	96.05934
2007	96.98175
2008	97.56414
2009	97.482
2010	97.25467
2011	97.38063
2012	97.69174
2013	97.70043
2014	97.64411
2015	98.06739
2016	98.29369
2017	98.76482