Year	% net
1977	80.49556
1979	80.48634
1980	79.70358
1981	80.31429
1982	81.07884
1983	83.40437
1984	83.13238
1985	82.20806
1986	82.24351
1987	82.50976
1988	83.57917
1989	84.0704
1990	84.59661
1991	86.52899
1992	87.54688
1994	92.2758
1995	89.88125
1996	93.05111
1997	91.59493
2013	94.64403
2014	94.71184
2015	95.32172
2016	96.10406
2017	96.86035