Year	% of total
1960	31.127975058249756
1961	30.45454771850582
1962	29.092680977442708
1963	28.16954594052783
1964	26.758741136526858
1965	27.50460444587614
1966	26.937153498708398
1967	26.01879920049083
1968	24.470185779818046
1969	23.514462098647353
1970	22.153361275791703
1971	22.19933652350194
1972	21.494212750842916
1973	19.922389577537775
1974	21.835705786079913
1975	21.46972390938672
1976	19.17663723955109
1977	18.5302294992287
1978	19.044912821626607
1979	19.1571181061517
1980	18.574867423701598
1981	18.56955921064139
1982	19.2055689509056
1983	19.422613200531806
1984	18.455855204295325
1985	17.69898317741877
1986	17.37496763097879
1987	16.41338278938399
1988	15.785522442616957
1989	14.581788948164503
1990	14.780785422974722
1991	14.92659370984469
1992	14.598325041018018
1993	15.021058433252238
1994	14.239540073031487
1995	14.69539022181917
1996	14.584314555308369
1997	14.446799810510319
1998	13.712834373496339
1999	13.36042015758689
2000	13.070512096206272
2001	12.3409208622193
2002	12.351516184910777
2003	11.963690258562837
2004	11.834539154294344
2005	11.68770713399583
2006	11.671454273066919
2007	11.242493977045399
2008	11.573312479681414
2009	11.994144574945116
2010	11.546139390964628
2011	11.832000737833035
2012	11.824781099777262
2013	12.087927269978918
2014	12.04794899348693
2015	11.584904311470801