Year	% net
1970	38.77498
1971	38.43226
1972	39.12789
1973	41.12648
1974	41.10255
1975	42.1113
1976	43.59118
1977	44.44373
1978	44.67011
1979	46.70457
1980	49.82468
1981	52.92345
1982	52.45953
1983	53.76728
1984	54.23408
1985	53.87825
1986	54.70658
1987	53.53879
1988	53.97712
1989	52.80778
1990	50.65855
1991	54.64197
1992	54.10509
1993	54.50937
1994	55.13633
1995	55.17728
1996	53.90937
1997	53.04164
1998	52.31906
1999	51.63462
2005	61.05424
2006	62.92962
2007	64.73444
2008	67.32392
2015	72.23039
2016	72.67399
2017	72.52852
2018	73.03517