Year	% of total
1971	66.37554585152839
1972	61.05585309869931
1973	41.460869565217386
1974	43.57887874837027
1975	31.079840929947995
1976	27.66842251178264
1977	34.07388916625062
1978	32.26982680036463
1979	32.78756476683938
1980	28.87364208118925
1981	17.877094972067038
1982	9.308380797396257
1983	7.194137002692193
1984	5.28825314260945
1985	6.616746085772634
1986	8.281813498196806
1987	10.311211098612674
1988	10.418521816562778
1989	12.821365248226952
1990	12.671375155795598
1991	13.3188484519283
1992	9.91871591727544
1993	4.470232088799193
1994	7.323452484742806
1995	5.052927555408535
1996	15.608550007975754
1997	15.324063856396675
1998	13.702961135101788
1999	6.397828615742536
2000	5.581901578169945
2001	5.788913997075635
2002	5.579258286839514
2003	8.782724092170346
2004	9.082180175091782
2005	5.075168481078278
2006	5.024164317358035
2007	4.5986832185756645
2008	4.5184824902723735
2009	12.144715062662568
2010	14.65021966880703
2011	8.022074702071503
2012	5.9667093469910375
2013	9.306016447843025
2014	5.694705350309608
2015	6.116158338741077