Year	% net
1971	88.12268
1972	88.34859
1973	88.90424
1974	88.9236
1975	89.00139
1976	89.60592
1977	90.2138
1978	90.39593
1979	91.26425
1980	93.35795
1981	93.52896
1982	94.26993
1983	94.04452
1984	94.1478
1985	94.10581
1986	94.83238
1987	95.63342
1988	96.11324
1989	96.03774
1990	96.35011
1991	96.22538
1992	95.88105
1993	95.47947
1994	95.13489
1995	95.26923
1996	95.18874
1997	94.73752
1999	95.87039
2001	96.22268
2004	95.89573
2005	96.19501
2006	96.51949
2007	96.73176
2008	96.86444
2009	96.47351
2010	95.98933
2011	95.93779
2012	95.63816
2013	95.73132
2014	95.87358
2015	96.1686
2016	96.24898
2017	95.70477
2018	95.53972