Year	% net
1978	30.79668
1979	33.37273
1980	34.55714
1981	35.8958
1982	37.68492
1983	39.6866
1984	40.5414
1985	41.26483
1986	45.90351
1988	46.55237
1989	45.73823
1990	44.89651
1992	44.35208
1994	45.11194
1996	49.56361
1997	53.91847
1998	56.60291
1999	55.59791
2000	58.41913
2003	65.22677
2004	63.67749
2005	64.73078
2006	66.88066
2007	69.34496
2008	70.19467
2009	70.56057
2010	71.57491
2011	72.23795
2012	74.27161
2013	73.18084
2014	73.74412
2015	73.84804
2016	73.53294
2017	75.3821