Year	% of total
1971	46.332033892844485
1972	44.67986030267753
1973	43.63611859838275
1974	40.76956861214132
1975	34.45041435206265
1976	36.19013551047892
1977	36.72477467995943
1978	28.517283733988418
1979	28.966739147942338
1980	25.217287416743822
1981	33.62357669122572
1982	28.58534879072556
1983	25.324572224189946
1984	27.1413781203267
1985	28.215165234597638
1986	20.606584718018407
1987	17.63331474394723
1988	18.976534197447705
1989	20.672868612208486
1990	20.268135397152896
1991	16.99774441938244
1992	19.696832851637765
1993	19.33693513079242
1994	13.625952382570633
1995	18.081025694918818
1996	19.938994616052913
1997	15.780360970309207
1998	13.507657539055643
1999	17.11764398725915
2000	16.10939589157652
2001	13.319438473185413
2002	11.43382167619065
2003	8.415990381725278
2004	10.609344944714058
2005	11.049655458431697
2006	11.809838558273404
2007	10.306402484996532
2008	14.55321835025899
2009	9.978562411766024
2010	13.475867124923333
2011	11.97254509481389
2012	10.377634850990145
2013	9.417945285646057
2014	12.900005306869744
2015	9.903965442986713