Year	% net
1971	43.71981
1972	44.01856
1973	44.82354
1974	45.99857
1975	56.40541
1976	56.76356
1977	57.77813
1982	66.54351
1983	66.29177
1984	67.01512
1986	68.02655
1987	67.93673
1988	62.72063
1996	72.18904
1997	72.22436
1999	86.34074
2000	86.45438
2001	83.96892
2002	82.71069
2003	82.62124
2004	82.14701
2005	85.63554
2006	85.59362
2007	85.78138
2008	86.34248
2010	88.45178
2011	88.29036
2012	87.61998
2013	87.16007
2014	86.82422
2015	86.40325
2016	86.34294
2017	85.22662