Year	% of total
1971	6.869070208728653
1972	6.858687389137597
1973	9.045531197301855
1974	4.413424413424413
1975	6.520874751491054
1976	6.380585716139637
1977	5.228119005529018
1978	2.948270390352269
1979	3.51685393258427
1980	6.662370095867236
1981	6.292436640386002
1982	6.057232966931033
1983	8.779938587512794
1984	24.871766280107046
1985	30.40839898632924
1986	27.263479145473042
1987	20.024211742695208
1988	22.121478246421873
1989	18.866535033886546
1990	16.76077858234239
1991	14.427619089664914
1992	13.88862094466416
1993	21.876463802565805
1994	25.937167725822803
1995	27.22329260954295
1996	28.33098886996866
1997	31.197943398435036
1998	37.17423600794191
1999	35.879641420058064
2000	38.60830566396096
2001	39.926310988332034
2002	40.58107239451311
2003	39.10999997086171
2004	38.804785440738435
2005	38.36065320181296
2006	38.01277748775698
2007	40.08029959732804
2008	43.19564081309017
2009	46.24199647534959
2010	44.14496756711051
2011	43.172138224373285
2012	45.08028289715313
2013	41.42883967197815
2014	42.40967563467957
2015	43.07625640446738