Year	% net
1971	12.94044
1972	13.21261
1973	14.26398
1974	14.91034
1975	15.91601
1976	16.89217
1977	18.87205
1978	20.52613
1979	23.04455
1980	26.81321
1981	33.69399
1982	37.2003
1983	40.65948
1984	43.92074
1985	46.41071
1986	46.88955
1992	39.86916
1993	43.12576
1996	51.79961
1998	54.33503
1999	62.88655
2000	60.67818
2001	61.51654
2002	59.32819
2003	64.01466
2004	65.82714
2005	64.42384
2006	68.95071
2007	68.68118
2008	66.30377
2010	64.44951
2011	66.9375
2012	69.6689
2013	68.08046
2014	71.44184
2015	75.00634
2016	77.15239
2017	79.84201
2018	80.63495