Year	% of total
1960	60.49762483322269
1961	58.65194273794734
1962	56.5696002468376
1963	58.187424452072555
1964	56.85607662659121
1965	56.89427222622877
1966	59.01729394955597
1967	58.20607970228454
1968	57.77258009102303
1969	60.79059758636076
1970	63.01105148180631
1971	61.06634511490176
1972	60.82285047598505
1973	59.273300910849315
1974	57.17783656781723
1975	57.856347808592766
1976	56.74258262878568
1977	58.95527015915481
1978	59.755902965105776
1979	57.17117537441621
1980	57.84799390809562
1981	54.84309783455138
1982	54.062938277424834
1983	52.95456054817104
1984	52.90660572094087
1985	52.15408157406895
1986	55.48632704886024
1987	53.79633919425145
1988	51.78077123808406
1989	53.37572015413918
1990	52.0530053123507
1991	52.94426708066512
1992	53.59213645053023
1993	54.758248152746894
1994	53.372501535781105
1995	53.03900925557243
1996	52.457211036702176
1997	54.566814486099915
1998	54.03449738837062
1999	55.195822266288275
2000	54.344018853171114
2001	55.656292067344815
2002	53.53006357273661
2003	58.88828460209561
2004	55.891555972885484
2005	54.98216280325153
2006	56.68576091744204
2007	56.18881465161404
2008	61.670896904400195
2009	63.11011116181548
2010	63.04306399544679
2011	57.32151682512342
2012	57.80716859421601
2013	61.84011850701244
2014	57.9782333483243
2015	56.951628649981146