Year	% net
1972	36.81372
1973	38.04833
1974	39.1471
1975	41.1056
1976	43.21056
1977	45.10238
1978	46.66082
1979	47.67807
1980	49.42365
1981	50.49992
1982	49.47292
1983	50.24488
1984	50.00898
1985	49.58962
1986	49.5523
1987	48.75066
1988	48.89961
1989	48.20071
1990	47.19032
1991	48.38723
1992	47.47905
1993	47.24732
1994	48.2967
1995	50.45865
1996	50.59386
1997	53.4049
1998	53.60959
1999	53.35461
2000	55.62006
2001	57.94914
2002	61.86638
2009	78.17549
2015	80.71093
2016	80.90068
2017	80.80115