Year	% net
1970	30.80284
1971	29.09711
1972	32.01279
1973	35.82015
1974	35.41899
1975	38.08784
1976	39.92616
1977	42.05371
1978	43.284
1979	44.60698
1980	46.44432
1981	47.83741
1982	47.12889
1983	47.29298
1984	47.86522
1985	47.45315
1986	47.59928
1987	47.30039
1988	49.93908
1989	49.94334
1990	49.38188
1991	51.08116
1992	51.40712
1993	51.48519
1994	52.46394
1995	53.53179
1996	53.74724
1997	55.68291
1998	55.92036
1999	56.04075
2000	58.29941
2001	60.2395
2002	63.48551
2003	65.98163
2004	68.56368
2006	73.05333
2007	74.55365
2008	76.62092
2009	77.24479
2010	77.18744
2011	78.36769
2012	79.21669
2016	79.95426
2017	79.6228
2018	79.50888