Year	% net
1973	67.87061
1974	71.78052
1975	74.18978
1976	76.1599
1977	77.72608
1978	78.77859
1979	78.87035
1980	79.98721
1981	80.25392
1982	79.92768
1983	79.26301
1984	80.29434
1985	80.65069
1986	81.81824
1987	83.14107
1988	84.25691
1989	85.33525
1990	85.87007
1991	87.60795
1992	88.70739
1993	88.22298
1994	88.16877
1995	88.39232
1996	87.9189
1997	87.36391
1999	88.62222
2000	89.39816
2001	91.25702
2002	92.17384
2003	92.40589
2004	92.86403
2005	93.09766
2006	93.20169
2007	95.24939
2008	96.36304
2009	97.44184
2010	97.23353
2011	97.5945
2012	97.31376
2015	97.54838
2016	97.5908
2017	97.5883
2018	97.63517