Year	% of total
1960	10.458410698862334
1961	10.602078700490484
1962	10.750880779291387
1963	10.892928112152985
1964	10.909215261177033
1965	10.320461677660411
1966	10.92595943569795
1967	10.928126772570709
1968	11.727543492660313
1969	12.018084249824229
1970	12.750272945491808
1971	12.828361359435492
1972	12.50745337407955
1973	11.528381738577615
1974	11.632671565118505
1975	11.285253354064395
1976	10.586562099219323
1977	10.532775363273652
1978	10.370434127610178
1979	10.935303467842106
1980	10.834824048843778
1981	10.362574467288086
1982	9.737978841195675
1983	9.097970377885558
1984	9.739132382062865
1985	9.219044703804363
1986	8.48892748405856
1987	8.90340934336347
1988	8.383128989598893
1989	9.835065550690738
1990	10.163266070666173
1991	10.408608123932746
1992	10.6751664985496
1993	11.02367594478899
1994	11.993977018536048
1995	12.546214999890182
1996	12.31474694705668
1997	13.388711568929763
1998	14.211835580983005
1999	15.2732605569646
2000	15.80188662456383
2001	16.715433288105398
2002	17.47277013333035
2003	17.6875900603332
2004	18.477425867663587
2005	19.006495443831167
2006	20.189434696164987
2007	21.589459810902053
2008	22.105211717753427
2009	22.98289694281462
2010	23.6322159797896
2011	24.442874073271568
2012	25.496894361576427
2013	24.292031163858006
2014	24.284062530814797
2015	26.15999074430992