Year	% net
1977	33.38151
1978	33.3322
1979	33.48067
1980	33.39035
1981	33.36161
1982	33.50469
1983	33.85856
1984	34.07453
1985	34.3631
1986	34.37366
1987	34.02835
1988	33.9646
1989	34.22738
1990	35.71382
1991	37.02097
1992	37.71779
1993	38.65307
1994	38.98886
1995	39.84991
1996	40.59934
1997	41.45159
1998	41.64523
1999	41.91999
2000	43.11165
2001	43.84274
2002	45.45982
2003	46.56596
2004	48.0463
2005	49.12939
2006	49.27895
2007	49.74518
2008	50.02595
2009	51.03843
2010	51.60479
2011	51.48634
2012	52.12797
2013	52.39899
2014	52.93968
2015	53.25687
2016	53.59265
2017	54.08654