Year	% net
1971	63.38682
1972	65.28022
1973	69.69175
1974	72.93361
1975	75.54909
1976	77.24009
1977	78.11463
1978	78.65693
1980	79.9479
1982	82.70063
1991	78.04497
1992	79.51083
1995	82.85109
1996	82.53367
1997	81.64421
1998	88.22536
1999	90.01793
2000	90.36688
2001	90.54107
2002	91.59308
2003	92.27449
2004	93.2769
2005	93.59603
2006	93.78802
2007	94.91267
2008	94.53881
2009	95.8761
2010	96.66345
2012	98.01034
2014	98.07109
2015	98.10531
2016	98.14067
2017	98.6613