Year	% of total
1971	16.14265603003285
1972	9.55898813521379
1973	13.997262149212869
1974	11.412283532322256
1975	9.18460833715071
1976	10.6607739570982
1977	10.842880523731587
1978	11.592664092664092
1979	14.505119453924914
1980	16.083737554250703
1981	16.062781766572048
1982	9.620082554123494
1983	10.804816223067174
1984	15.559013114025339
1985	12.286324786324785
1986	10.750135648399349
1987	9.835646223700198
1988	17.83624002364765
1989	30.352029644601654
1990	35.51600261267146
1991	21.291518460998947
1992	11.630818763135537
1993	11.869349664625254
1994	18.566285556039087
1995	22.803011381881756
1996	30.9081443399603
1997	28.152686428206746
1998	31.941198006139288
1999	33.26387079968742
2000	21.12630370776985
2001	11.372880957419294
2002	11.568317647867007
2003	10.416622178564564
2004	15.071863771285738
2005	13.741330691258288
2006	19.15943600867679
2007	22.66147088482114
2008	23.636607262494973
2009	24.533118144988634
2010	27.908131184432605
2011	29.85558413099387
2012	36.32492724118651
2013	41.38096215698351
2014	36.33848475533074
2015	37.14433523021211