Year	% net
1971	67.2291
1972	70.65703
1973	72.44004
1974	72.5405
1975	75.90756
1976	73.8364
1977	73.57305
1978	72.7629
1979	74.97447
1980	78.13813
1981	78.47891
1982	76.92443
1983	80.67743
1984	85.49123
1985	91.3604
1986	95.87053
1987	96.04177
1988	97.88943
1989	98.79704
1992	97.96123
1993	98.80626
1994	99.01581
1995	99.9328
2001	95.6837
2002	95.05905
2003	94.70552
2004	93.73391
2005	91.15046
2006	93.4615
2011	91.16974
2012	91.84122
2013	92.73228
2014	94.69685
2015	96.75294
2016	96.98251
2018	95.85031