Year	% net
1970	15.80445
1971	15.96762
1972	17.93135
1973	19.39772
1974	20.42732
1975	22.31724
1976	24.18791
1977	26.08274
1978	28.03175
1979	29.17821
1980	30.0819
1981	30.78899
1982	32.03098
1983	33.00435
1984	34.09824
1985	35.27775
1986	37.21995
1987	38.71607
1988	39.71158
1989	41.06671
1990	43.81961
1991	44.53185
1992	44.70194
1993	46.32716
1994	48.93851
1995	49.68187
1996	50.37218
1997	52.23651
1998	53.97258
1999	55.795
2000	57.00151
2001	57.86574
2002	58.60007
2003	59.7622
2004	60.86467
2005	60.89001
2006	61.25071
2007	60.82806
2008	62.26326
2009	64.17043
2010	64.36491
2011	67.18807
2012	67.64223
2013	64.5343
2014	64.86205
2015	65.66358
2016	66.66874
2017	67.3266
2018	67.83314