Year	% net
1970	68.00887
1971	67.95768
1972	69.06265
1973	71.68667
1974	72.63647
1975	73.96798
1976	74.67202
1977	74.70059
1978	73.51313
1979	73.92034
1980	74.8703
1981	75.91557
1982	76.38909
1983	76.8235
1984	77.22085
1985	77.99156
1986	78.79348
1987	79.03782
1988	79.74049
1989	80.47319
1990	80.11854
1991	80.48952
1992	80.30372
1993	80.41438
1994	80.45414
1995	80.00896
1996	79.723
1997	79.78869
1998	80.39454
1999	81.18966
2000	81.87006
2001	82.11577
2002	82.40194
2003	83.83159
2004	85.09061
2005	85.76534
2006	86.2096
2007	87.55165
2008	87.76107
2009	87.77482
2010	87.81299
2011	87.86107
2012	88.23096
2013	88.24385
2014	88.47975
2015	88.37306
2016	88.5905
2017	88.44634
2018	88.61307