Year	% net
1975	37.09122
1976	38.05963
1977	40.38819
1978	42.77687
1979	45.86792
1980	48.72234
1981	51.47439
1982	53.30328
1983	53.7083
1984	53.07665
1985	51.85113
1986	50.15244
1987	48.85114
1988	48.11084
1989	48.52779
1990	47.9399
1991	49.20902
1992	49.20663
1993	49.86054
1994	50.24699
1995	50.8604
1996	49.35542
1997	52.26143
1998	53.25993
1999	54.38131
2000	56.547
2001	58.32576
2002	59.83147
2003	62.38962
2004	64.4125
2005	66.64634
2006	68.66341
2007	70.66965
2008	72.03598
2009	72.41189