Year	% net
1970	17.70158
1971	17.82773
1972	19.59582
1973	20.94308
1974	21.9083
1975	23.66734
1976	25.4167
1977	27.21097
1978	29.00194
1979	30.07824
1980	31.04123
1981	31.81309
1982	33.09011
1983	34.13931
1984	35.26792
1985	36.4819
1986	38.34212
1987	39.78736
1988	40.80874
1989	42.17278
1990	44.75599
1991	45.46037
1992	45.64418
1993	47.32005
1994	49.87864
1995	50.74646
1996	51.55383
1997	53.38863
1998	55.11159
1999	56.93202
2000	58.20964
2001	59.14554
2002	59.98598
2003	61.20917
2004	62.41996
2005	62.62322
2006	63.09084
2007	62.86044
2008	64.33042
2009	66.19974
2010	66.57702
2011	69.24243
2012	69.84937
2013	67.38518
2014	67.90363
2015	68.66013
2016	69.57428
2017	70.24928
2018	70.76348