Year	% net
1971	51.57357
1972	60.08427
1973	61.65289
1974	62.86412
1975	69.59258
1976	71.95016
1977	68.7854
1978	66.51193
1979	64.37794
1980	67.6333
1981	65.16347
1982	70.91504
1983	74.00655
1984	76.12158
1985	75.97463
1986	73.8507
1987	72.86538
1988	73.11098
1989	75.20883
1990	77.43415
1991	78.06332
1992	80.7998
1993	80.7028
1994	80.58905
1995	81.25474
1996	79.82394
1997	80.77807
1998	80.31158
1999	80.11768
2000	82.02675
2001	81.0434
2002	82.09974
2003	86.26731
2004	87.59445
2005	87.58097
2006	85.29509
2008	80.24937
2010	83.80971
2012	88.90797
2013	87.85101
2014	88.22941
2015	88.88531
2016	89.55552
2017	92.96077