Year	% of total
1971	37.72044364036813
1972	38.42533527741074
1973	37.6515785955438
1974	37.32112571793705
1975	36.869218362372614
1976	41.327309611489746
1977	37.176023997515586
1978	38.217069023687124
1979	36.870637085773886
1980	37.649207614388466
1981	38.15838283285986
1982	39.5423432838685
1983	43.96831525556401
1984	40.384531584480385
1985	41.0076139376523
1986	38.41906070995109
1987	37.68925001079093
1988	34.336395695132836
1989	35.03900975923593
1990	34.255400494608715
1991	35.20603670389932
1992	33.018620476490135
1993	32.096230192724725
1994	20.371550240307187
1995	29.647742822307926
1996	22.034103963144823
1997	18.56354687678743
1998	15.82491489760171
1999	16.683825627654276
2000	26.22458696779138
2001	29.3769619954106
2002	24.25694894954838
2003	32.509498468193605
2004	32.29916434207618
2005	33.30971620803436
2006	28.974432541145568
2007	35.15468123237028
2008	35.49801145508677
2009	40.25490475011967
2010	42.042991900405156
2011	36.59055251768788
2012	41.47229036101685
2013	41.60714156466672
2014	40.480603383492266