Year	% of total
1971	39.56043956043956
1972	39.73747016706444
1973	42.730299667036626
1974	32.89205702647658
1975	29.622815087396503
1976	44.95699765441751
1977	29.40226171243942
1978	20.436507936507937
1979	15.267175572519085
1980	26.380368098159508
1981	17.57894736842105
1982	15.899795501022496
1983	7.957302280446385
1984	10.653409090909092
1985	5.981067125645438
1986	10.430930326218284
1987	13.540197461212976
1988	4.256756756756757
1989	3.520671834625323
1990	7.14064914992272
1991	4.6592894583576
1992	4.286964129483815
1993	3.622787610619469
1994	5.736137667304015
1995	10.16866291860181
1996	9.497076023391813
1997	16.566466265865063
1998	18.01645734084019
1999	33.619327161887554
2000	53.020469296055914
2001	33.40717766947275
2002	21.98322219832222
2003	16.385880465302847
2004	25.01396908176569
2005	28.33763996554694
2006	29.65912711054476
2007	28.39944435869733
2008	36.869300911854104
2009	44.708487084870846
2010	30.930484176359208
2011	33.12701482914249
2012	25.223460266927884
2013	30.71203244704822
2014	18.513717865629726
2015	12.4857527717335