Year	% net
1973	40.33013
1974	42.18452
1975	43.66042
1976	45.13146
1977	47.89637
1978	51.26766
1979	55.02263
1980	56.64861
1981	57.93572
1982	58.31462
1983	58.81732
1984	58.51164
1985	57.32741
1986	55.66359
1987	54.3324
1988	53.60678
1989	52.42029
1990	52.19145
1991	53.0951
1992	52.53111
1993	53.21314
1994	53.47561
1995	54.15415
1996	52.13494
1997	55.1938
1998	55.80002
1999	56.38184
2000	58.20837
2001	59.95785
2002	62.59331
2009	73.57617
2018	76.64759