Year	% net
1971	46.03706
1972	45.27388
1973	52.14207
1975	58.13073
1976	61.53776
1977	64.58672
1978	66.315
1979	69.11859
1980	72.43316
1981	73.5598
1999	87.22194
2000	88.76119
2001	90.33215
2002	90.92089
2003	91.28496
2004	92.41558
2005	93.27141
2006	92.8639
2007	92.07332
2008	91.50683
2009	91.07021
2010	90.86856
2011	89.39714
2012	89.80611
2013	90.5337
2014	91.42704
2015	92.77119
2016	94.94198
2017	96.87779