Year	% net
1970	58.2604
1971	58.15917
1972	60.17833
1973	63.10961
1974	64.65359
1975	67.32145
1976	68.20821
1977	69.14835
1978	69.5151
1979	70.30472
1981	74.06974
1982	73.00019
1983	72.17532
1984	71.76853
1985	73.35026
1986	72.29966
1987	73.23367
1988	72.49306
1989	72.44472
1990	74.27921
1991	74.47759
1992	75.68573
1993	75.3296
1994	77.80021
1995	80.63427
1996	79.92177
2009	81.5829
2010	87.16025
2011	86.26999
2012	86.57568
2013	83.63544
2014	84.51263
2015	83.54355
2016	83.62154
2017	82.37601