Year	% net
1978	79.68499
1980	76.15229
1981	73.20257
1982	78.237
1983	73.66271
1984	73.48471
1985	73.12173
1986	73.86725
1987	84.85019
1988	88.24281
1989	93.00106
1990	96.9068
1991	97.42814
1992	93.98811
1993	90.43338
1994	88.41546
1995	88.89034
1996	86.05468
1997	82.45285
1998	79.37283
2007	86.66614
2012	86.53352
2013	85.55659
2014	90.21069
2015	93.73636
2016	94.55178
2017	95.02753