Year	% net
1971	37.93928
1972	39.25104
1973	40.74558
1974	42.65279
1975	45.84587
1976	47.11695
1977	49.95725
1978	52.3959
1979	54.85764
1980	57.54774
1981	59.0857
1983	61.99498
1984	63.23861
1985	65.48248
1996	75.42427
2001	72.03643
2002	72.193
2003	72.56144
2004	73.56278
2005	74.49569
2006	75.10634
2007	76.58814
2008	77.74197
2009	78.5706
2010	79.58861
2011	78.2114
2012	89.45403
2013	88.19284
2014	88.27593
2015	88.66643
2016	90.65574
2017	93.28205
2018	95.76465