Year	% of total
1971	43.10679611650485
1972	43.10679611650485
1973	41.73789173789174
1974	35.95868302130407
1975	32.63675476336817
1976	32.78688524590164
1977	30.868665977249226
1978	33.84407390716539
1979	29.933388842631143
1980	26.60433489162771
1981	26.070623591284747
1982	24.86824769433465
1983	18.409554325662686
1984	18.532526475037823
1985	19.434628975265017
1986	27.458333333333336
1987	15.052801145516378
1988	12.092952147989603
1989	8.193956430077302
1990	4.306777030522504
1991	1.765417170495768
1992	4.452439847087924
1993	6.789050619161416
1994	6.704824202780049
1995	8.532296872108088
1996	6.458079135436639
1997	9.428234103558779
1998	8.702064896755163
1999	9.266435986159168
2000	6.46756705345254
2001	6.7387304507819685
2002	6.7398874899544605
2003	6.742086038961038
2004	5.862334400194466
2005	5.7700306272923205
2006	5.553486167078663
2007	5.299145299145299
2008	4.196621661114033
2009	4.325254861876967
2010	3.6234371169404263
2011	9.491993749009128
2012	12.336806556566863
2013	12.59789156626506
2014	14.69961500581968
2015	16.37999694972124