Year	% net
1971	100
1972	99.90995
1973	96.35086
1974	99.34907
1975	100
1976	98.85311
1980	97.22125
1981	100
1984	95.93899
1992	88.52849
1993	88.8667
1994	92.60562
1999	90.54622
2004	88.80686
2005	90.23928
2006	86.01952
2007	86.93278
2008	85.77192
2009	81.81508
2010	80.42244
2011	85.58313
2012	79.93012
2013	74.72864
2014	75.44279
2015	79.81499
2016	75.35743
2018	74.22717