Year	% of total
1960	17.056277056277054
1961	19.909159727479185
1962	22.293447293447294
1963	22.941801587797713
1964	31.94514132798127
1965	32.10929759607863
1966	33.29671864091227
1967	38.22933333333333
1968	42.69718698290127
1969	53.11397234144015
1970	59.2446448703495
1971	62.627317837555495
1972	66.71364810899695
1973	73.23646771396709
1974	65.51547564861174
1975	63.81074763392272
1976	63.3195395588096
1977	64.40983733525259
1978	58.492717454443756
1979	52.95708477124407
1980	46.23435237567922
1981	45.26776913055166
1982	41.15055104939573
1983	38.351410825661794
1984	32.83982970627597
1985	27.567655909593203
1986	26.75442256341789
1987	26.950355604611993
1988	28.187025069004925
1989	29.377649823292618
1990	21.811411747312786
1991	20.695147575119517
1992	21.00940402267893
1993	18.579292370614244
1994	18.984168486380877
1995	17.309467632576762
1996	15.912300172608868
1997	14.974244215504138
1998	14.147960932554327
1999	14.222481911487787
2000	13.227557963848646
2001	12.009414610564747
2002	13.21931038525334
2003	14.113397102629097
2004	12.604712678680507
2005	12.565202569585562
2006	10.683812477717728
2007	11.612413787124098
2008	10.759391934293014
2009	7.612819166411605
2010	6.868561764953547
2011	10.621066965253869
2012	12.706505197646864
2013	10.203338162359081
2014	8.535860059968336
2015	7.519420129705795