Year	% net
1977	79.91926
1979	79.4043
1980	78.91019
1981	79.45693
1982	79.8442
1983	82.46216
1984	82.48874
1985	81.4349
1986	81.89552
1987	82.18164
1988	83.54502
1989	83.95752
1990	84.29273
1991	86.33583
1992	87.38961
1994	90.69946
1995	89.35682
1996	92.20469
1997	90.97443
2013	93.71201
2014	93.72766
2015	94.41834
2016	95.27158
2017	96.04486