Year	% net
1971	74.91528
1972	75.79483
1973	75.95367
1974	74.78064
1975	75.52789
1976	78.19822
1977	79.39524
1978	80.80097
1979	81.7203
1999	85.4531
2000	87.62264
2001	90.0761
2002	93.00095
2003	91.54203
2004	91.64917
2005	90.65024
2006	90.74801
2007	91.95035
2008	90.00491
2009	92.01323
2010	92.48108
2011	92.69816
2012	92.49758
2013	91.56032
2014	91.1096
2015	90.69857
2016	88.88692
2017	87.39174