Year	% net
1972	20.52918
1973	22.40579
1974	26.31302
1979	61.1609
1986	70.83282
1987	69.5071
1988	70.30375
1989	72.59362
1990	71.17462
1991	73.50074
1992	72.11035
1994	63.94686
1999	79.17534
2000	81.51485
2001	83.72802
2002	82.47511
2003	84.78699
2004	86.19459
2005	87.88753
2006	90.24181
2007	89.72188
2008	88.66904
2009	86.9229
2010	88.86108
2011	88.60291
2012	87.68415
2013	87.9858
2014	86.3748
2015	85.6546
2016	86.31438
2017	86.37745
2018	86.70001