Year	% net
1970	64.21323
1971	63.8255
1972	64.85866
1973	67.83525
1974	68.7001
1975	70.24341
1976	70.8253
1977	70.58396
1978	68.86952
1979	69.03861
1980	70.41066
1981	71.56029
1982	72.06261
1983	72.47761
1984	72.94341
1985	74.01937
1986	75.27758
1987	75.79281
1988	76.60216
1989	77.56444
1990	77.24896
1991	77.75459
1992	77.6501
1993	77.9925
1994	78.25015
1995	77.97821
1996	77.91187
1997	78.14253
1998	78.88847
1999	79.89925
2000	80.68304
2001	81.01112
2002	81.39747
2003	83.53928
2004	84.72136
2005	85.44083
2006	86.01105
2007	87.16241
2008	87.62318
2009	87.85407
2010	87.88409
2011	88.06601
2012	88.19405
2013	88.20248
2014	88.33011
2015	88.17368
2016	88.33632
2017	88.17059
2018	88.2163