Year	% net
1975	37.10012
1976	38.06778
1977	40.3958
1978	42.784
1979	45.87415
1980	48.72755
1981	51.47926
1982	53.30791
1983	53.71269
1984	53.08083
1985	51.85551
1986	50.15715
1987	48.85559
1988	48.11508
1989	48.53196
1990	47.94427
1991	49.21324
1992	49.21065
1993	49.86441
1994	50.25112
1995	50.86447
1996	49.35954
1997	52.26508
1998	53.2634
1999	54.38436
2000	56.54948
2001	58.32808
2002	59.83408
2003	62.392
2004	64.41467
2005	66.64822
2006	68.665
2007	70.6711
2008	72.03732
2009	72.41319