Year	% of total
1971	10
1972	11.738746690203
1973	11.61400512382579
1974	11.940298507462686
1975	11.58129175946548
1976	11.28133704735376
1977	10.440251572327044
1978	10.691458454386984
1979	10.098792535675083
1980	12.72390364422483
1981	13.92896781354051
1982	10.470588235294118
1983	11.610700056915196
1984	13.082039911308204
1985	10.97972972972973
1986	11.153427638737758
1987	8.596300326441785
1988	6.0606060606060606
1989	5.963740458015267
1990	8.610990913024665
1991	2.9437609841827768
1992	5.4311774461028195
1993	2.036967182195398
1994	2.0184135977337108
1995	2.2192779065915866
1996	1.5750463248919087
1997	1.1520737327188941
1998	1.9137466307277629
1999	1.9067250708580261
2000	0.7731958762886598
2001	1.1809045226130652
2002	1.218929254302103
2003	1.3157894736842104
2004	1.2602255140393543
2005	1.3071895424836601
2006	1.6603773584905661
2007	1.7614230903383328
2008	1.684717208182912
2009	1.6990687796111748
2010	1.9330087059170724
2011	1.5927977839335181
2012	2.0232345646782406
2013	1.8350898946063237
2014	1.9988577955454025
2015	2.25140712945591