Year	% net
1972	38.03401
1973	38.87528
1974	39.53972
1975	41.23974
1976	43.0989
1977	44.61937
1978	45.96097
1979	47.06466
1980	48.66584
1981	49.81435
1982	49.15357
1983	49.89269
1984	49.6742
1985	49.47428
1986	49.44099
1987	48.7459
1988	48.64043
1989	47.47732
1990	46.28102
1991	47.48325
1992	46.50594
1993	46.32689
1994	47.33583
1995	49.32276
1996	49.36694
1997	52.39835
1998	52.72448
1999	52.55145
2000	54.52116
2001	56.94519
2002	60.34442
2009	76.35419
2017	80.59165
2018	80.40995