Year	% net
1971	33.87941
1972	35.30299
1973	37.22131
1974	39.62656
1975	43.02282
1976	45.34576
1977	48.34647
1978	51.56288
1979	55.39661
1980	58.50658
1981	60.87547
1983	65.0753
1984	66.39646
1985	68.429
1996	77.28146
2001	72.8222
2002	72.80981
2003	73.28081
2004	74.14769
2005	75.10865
2006	75.59361
2007	76.89025
2008	78.07838
2009	78.97387
2010	79.86728
2011	78.43632
2012	90.01135
2013	88.72314
2014	88.86817
2015	89.30273
2016	91.4471
2017	93.73494
2018	96.14117