Year	% net
1970	94.78505
1971	94.79381
1972	94.95411
1973	94.81346
1974	95.21968
1975	95.22927
1976	95.3675
1977	95.3606
1978	95.92637
1979	96.29604
1980	96.49627
1981	96.42319
1982	96.10532
1983	95.60779
1984	95.43535
1985	95.31872
1986	96.02723
1987	96.46
1988	96.49502
1989	96.57611
1990	96.25657
1991	96.14644
1992	95.13914
1993	95.49376
1994	95.03511
1995	95.75209
1996	96.83667
1997	97.3
1999	97.61867
2000	97.49598
2001	97.49529
2002	97.22747
2003	97.01571
2004	97.00405
2005	97.64336
2006	97.65115
2007	97.88234
2008	97.74909
2009	97.56059
2010	97.55384
2011	97.84549
2012	97.97542
2013	98.01133
2014	97.56492
2015	97.72417
2016	97.75038
2017	97.64662