Year	% of total
1971	42.59980624179124
1972	45.39297319857615
1973	42.613376807124574
1974	46.03415590467969
1975	44.31871603923991
1976	47.07522412606252
1977	45.938523931033735
1978	41.76468866294973
1979	42.52808782603275
1980	43.61478346829905
1981	45.76294744117801
1982	48.368141772610834
1983	48.565580252006704
1984	49.39059180241501
1985	53.09647958874019
1986	54.169505859794356
1987	58.332635370741905
1988	56.76476260449972
1989	57.77341355833613
1990	55.47364098530484
1991	56.86808329129239
1992	56.9054668718903
1993	58.827708298920555
1994	57.03011906817568
1995	59.07532423166254
1996	59.604804157468315
1997	58.42042044958544
1998	56.65856169013278
1999	57.175042177550004
2000	58.39072535663372
2001	58.92627208251857
2002	59.207548114683384
2003	57.447687395722625
2004	56.98276290442745
2005	55.93888605151264
2006	55.96825504376227
2007	55.55198345731608
2008	58.380764925020614
2009	57.344440273918195
2010	57.80822891143595
2011	57.96445982927867
2012	62.272998495453336
2013	62.92894750859864
2014	65.09801529355963
2015	66.06717867631143