Year	% of total
1971	39.53215922288234
1972	41.484298679046304
1973	42.00244569760494
1974	42.42215768698536
1975	42.28609831723867
1976	43.306446990619065
1977	44.17452220025411
1978	45.143861066985366
1979	46.84381975641208
1980	47.17179685152314
1981	47.592057482182845
1982	48.535868950595955
1983	49.180995538533374
1984	49.677146628772576
1985	49.366517260088344
1986	48.64965815223192
1987	47.96604646386728
1988	48.15179351084347
1989	47.399609757766726
1990	46.90177115801432
1991	46.15075639162253
1992	42.84619336666684
1993	40.57843204888495
1994	38.74210529751722
1995	38.041156152596024
1996	36.49402163736309
1997	36.458827799436186
1998	36.3498682622938
1999	37.41164815469931
2000	37.01713840842818
2001	37.007260468562926
2002	36.56259509373363
2003	36.6524652537755
2004	36.997287005598835
2005	38.841212559787664
2006	39.34808586938071
2007	38.14435260423227
2008	39.092236749893125
2009	35.48123891976006
2010	34.39125372394806
2011	20.47299123585911
2012	20.01392396889914
2013	26.02476192275148
2014	23.015227503601558