Year	% net
1970	26.69633
1971	26.8072
1972	28.59168
1973	30.59647
1974	31.58691
1975	33.71992
1976	35.86637
1977	38.13816
1978	40.15494
1979	41.47132
1980	42.37846
1981	42.82126
1982	44.08273
1983	44.89023
1984	45.77174
1985	46.81159
1986	48.67838
1987	49.84839
1988	50.36031
1989	51.32639
1990	53.95296
1991	54.21788
1992	53.7523
1993	55.04499
1994	57.4304
1995	57.90925
1996	58.32554
1997	59.73695
1998	61.41576
1999	63.10066
2000	64.3604
2001	65.26796
2002	66.0282
2003	67.0314
2004	68.452
2005	68.30876
2006	68.43767
2007	67.927
2008	69.37033
2009	71.25413
2010	71.045
2011	73.10258
2012	73.16594
2013	71.58968
2014	72.42768
2015	73.15713
2016	74.07489
2017	74.51229
2018	74.94981