Year	% of total
1960	18.439899009477553
1961	18.271231142023357
1962	18.88088527448022
1963	17.255415345442792
1964	17.160151817956677
1965	17.524136604910943
1966	16.249088334977905
1967	17.44788667511229
1968	15.92924126172208
1969	16.53080851693442
1970	15.424680597404627
1971	15.468891263253063
1972	14.639224378467178
1973	13.50204959631322
1974	15.535051485821283
1975	15.069760735098154
1976	13.402654964529221
1977	9.972837066295655
1978	12.226638957504656
1979	11.97548124456755
1980	11.48513587001302
1981	10.803791837913783
1982	13.140637918738049
1983	13.697244634632346
1984	12.656641848497701
1985	10.830194105179812
1986	11.128133092702114
1987	8.716624950730296
1988	7.292195146187495
1989	8.189588750996679
1990	8.528502912908122
1991	8.854523501562264
1992	7.7775097329325495
1993	8.353186771712979
1994	7.612425872653056
1995	8.827515039172386
1996	9.611080497496195
1997	9.072904128837598
1998	7.782749078460688
1999	7.174470097618828
2000	6.289399722048692
2001	4.90388870987027
2002	6.632079930478822
2003	6.871346940265359
2004	6.535987734084204
2005	6.382108498069872
2006	6.827327461847467
2007	5.772985824189421
2008	5.911010412205444
2009	6.616179257909514
2010	6.023062385933374
2011	7.436102190270268
2012	6.521155807556468
2013	6.3179099039587
2014	6.053798473590674
2015	5.841638259567964