Year	% net
1970	60.36817
1971	60.34406
1972	61.81542
1973	63.91866
1974	63.90678
1975	65.1643
1976	65.94492
1977	67.79014
1978	67.4348
1979	68.36012
1980	69.66101
1981	71.14686
1982	72.69978
1983	73.71603
1984	74.3534
1985	74.24502
1986	74.55926
1987	74.10391
1988	75.17135
1989	76.25231
1990	75.32242
1991	75.70541
1992	76.00001
1993	76.83693
1994	77.58304
1995	77.05635
1996	76.91215
1997	76.86086
1998	76.60374
1999	76.98358
2000	78.07473
2001	78.28473
2002	78.17578
2003	80.53365
2004	81.80227
2005	82.82935
2006	83.64591
2007	85.57255
2008	85.08569
2009	85.20267
2010	85.56855
2011	85.44397
2012	85.96188
2013	86.03915
2014	86.41458
2015	86.3574
2016	86.73376
2017	86.64486
2018	86.9201