Year	% of total
1971	30.751577739529544
1972	34.143449911084765
1973	23.597506678539627
1974	23.176361957525394
1975	17.557565789473685
1976	32.126696832579185
1977	16.332378223495702
1978	25.887265135699373
1979	25.89118198874296
1980	17.12707182320442
1981	41.224366706875756
1982	28.688805203697363
1983	27.57406864183045
1984	30.59166887768639
1985	27.40119760479042
1986	32.03143055234573
1987	32.91872185288441
1988	45.32967032967033
1989	14.562211981566819
1990	9.437533802055164
1991	13.01668806161746
1992	9.55025981006988
1993	21.090977022230526
1994	9.42862197063506
1995	11.027935000912908
1996	13.046107331821618
1997	9.190160309563295
1998	10.964119158656134
1999	14.017704864777064
2000	8.903639276722362
2001	7.2092478325392495
2002	8.699384747460295
2003	11.934385208869118
2004	16.301121372031663
2005	17.62868193989884
2006	15.230004144218814
2007	13.984151295198775
2008	11.461926240382065
2009	12.890403180011356
2010	11.74285145624627
2011	11.742071619189474
2012	12.948762635064481
2013	12.724998640491597
2014	8.968406748952553
2015	6.36614834480143