Year	% of total
1960	60.98407024327559
1961	61.522910778156096
1962	62.77537640262815
1963	63.52639595023668
1964	64.78105404211828
1965	64.18138295715852
1966	64.45047562930694
1967	65.20707535242872
1968	66.51905644520546
1969	67.31864422618169
1970	68.42107501823203
1971	70.07295426178973
1972	70.13581474581068
1973	70.8550387848351
1974	67.84177936775565
1975	66.21138010993732
1976	67.8144627659679
1977	66.95171068793681
1978	65.35302248606185
1979	65.29402884457573
1980	65.27805261035822
1981	63.52829296884103
1982	61.67264903144725
1983	60.21056627036909
1984	59.035593177439026
1985	57.3222043514947
1986	56.086424034166605
1987	56.32177038397811
1988	56.037173161432285
1989	56.918975316770926
1990	58.578687630963444
1991	58.17021385032813
1992	58.12288839804919
1993	57.46072579689868
1994	57.66536661595602
1995	57.07786000199297
1996	56.90204507138839
1997	57.87795830577211
1998	58.612277385627976
1999	58.62559915385733
2000	59.422299195933014
2001	59.61152678334148
2002	59.934384934097395
2003	60.86107267358173
2004	60.20612344981649
2005	60.38756478450542
2006	60.15734753953035
2007	61.20582166008972
2008	60.49570319833892
2009	58.96453469577148
2010	59.2183815508015
2011	59.3179666126989
2012	59.47496245130769
2013	58.22463638009736
2014	57.287384739499636
2015	56.73008767870592