Year	% of total
1971	48.735244519392914
1972	48.93617021276596
1973	43.65482233502538
1974	40.71550255536627
1975	39.61937716262976
1976	36.97916666666667
1977	30.939226519337016
1978	28.39506172839506
1979	29.87220447284345
1980	29.753265602322205
1981	29.680998613037445
1982	27.31829573934837
1983	26.744186046511626
1984	24.175824175824175
1985	23.986486486486484
1986	21.639344262295083
1987	19.170403587443946
1988	18.814139110604334
1989	17.974971558589306
1990	11.647254575707153
1991	10.504549214226634
1992	7.2522159548751
1993	8.676789587852495
1994	6.685044796691937
1995	6.4833005893909625
1996	5.801621958827199
1997	2.973977695167286
1998	2.9038112522686026
1999	1.1557177615571776
2000	1.3739545997610514
2001	0.9443339960238568
2002	1.0273972602739725
2003	0.6968641114982579
2004	0.7089405277668374
2005	0.421792618629174
2006	0.3059039461609055
2007	4.56723992106005
2008	12.364310299179243
2009	11.122244488977955
2010	0.6224899598393574
2011	0.5839646464646465
2012	0.15806111696522657
2013	0.09193288899103653
2014	0.03152916447714135
2015	0.03832518923062182