Year	% of total
1971	42.80854059127171
1972	35.224983210208194
1973	35.592060232717316
1974	31.05302785844896
1975	26.259734310581766
1976	28.0801983399806
1977	27.894844517184943
1978	29.131274131274132
1979	32.26154122507634
1980	32.124925538252064
1981	31.040240440808148
1982	23.7553702299722
1983	22.203738910012675
1984	24.6054678817515
1985	19.764957264957264
1986	17.864894194248507
1987	16.262710238536805
1988	23.82500738989063
1989	39.00398630060075
1990	46.16263879817113
1991	29.026601873653625
1992	17.305370478021732
1993	18.335208098987625
1994	25.73485777584365
1995	27.59481928140721
1996	39.54706667100511
1997	37.865273147731024
1998	51.829113745810915
1999	61.96926282886168
2000	51.45216827186986
2001	45.73840257694388
2002	44.549014219962906
2003	49.843045975784236
2004	53.09912513669739
2005	46.11691182074537
2006	44.74511930585683
2007	55.84440000683656
2008	54.250971459198716
2009	51.012812489707194
2010	59.61213886222987
2011	60.403573113387
2012	63.55464437785838
2013	64.10867036200644
2014	57.186373417544644
2015	56.39566503508563