Year	% net
1971	36.86046
1972	37.95453
1973	38.30772
1975	41.20807
1976	44.13876
1977	47.72865
1978	50.99459
1979	53.43977
1980	56.10223
1981	58.7991
1982	59.14966
1983	61.50494
1984	64.02097
1985	62.73205
1986	60.98054
1987	58.98187
1988	57.27868
1989	55.17983
1990	56.02291
1991	55.67112
1992	56.17062
1993	58.30964
1994	60.944
1995	63.7744
1996	66.10001
1997	67.70415
1998	66.98136
1999	71.79044
2000	76.57579
2001	80.44593
2002	84.58196
2003	85.84979
2004	85.71852
2005	86.73812
2006	87.99563
2007	89.26677
2008	89.83254
2009	89.52588
2010	92.28772
2011	93.22653
2012	92.48523
2013	93.19128
2014	93.26164
2016	94.61489
2017	96.89422
2018	99.09904