Year	% net
1977	33.64919
1978	33.55549
1979	33.56711
1980	33.34457
1981	33.34698
1982	33.6293
1983	33.96072
1984	34.14414
1985	34.4109
1986	34.41726
1987	34.04078
1988	33.94918
1989	34.20861
1990	35.60473
1991	36.76237
1992	37.47199
1993	38.43584
1994	38.70722
1995	39.48224
1996	40.20624
1997	41.12348
1998	41.48532
1999	41.80494
2000	43.11204
2001	43.99237
2002	45.55286
2003	46.64881
2004	48.30282
2005	49.35865
2006	49.39798
2007	50.30923
2008	50.51286
2009	51.25826
2010	51.6864
2011	51.62497
2012	52.43997
2013	52.7261
2014	53.1738
2015	53.35628
2016	53.6004
2017	54.02025