Year	% of total
1960	83.1924410253646
1961	83.65489981455934
1962	84.33321618984198
1963	85.34441854082124
1964	85.4201311056283
1965	86.21466224669635
1966	85.66560058786234
1967	85.79769942971703
1968	85.75814269594846
1969	85.260793354493
1970	84.66224172654242
1971	84.15415429868938
1972	84.02431777779947
1973	82.79334872359591
1974	82.20550434887467
1975	84.05443830445232
1976	83.30431309855587
1977	82.51579585190271
1978	81.22728546457533
1979	81.42941614957023
1980	80.56398301279715
1981	79.5138438623392
1982	79.06654510745994
1983	77.0090614433204
1984	76.8489240654414
1985	75.40659270372093
1986	73.56401828516171
1987	73.79490756364362
1988	74.02295138736808
1989	75.05195139374929
1990	73.60549156089368
1991	72.29038202158334
1992	73.4363630240629
1993	72.57768591582352
1994	71.69826660191809
1995	72.52018143855318
1996	73.23708495477278
1997	74.73610579933592
1998	75.88275617826282
1999	75.63775472582364
2000	76.10257181165409
2001	76.15495344009172
2002	75.16336686415079
2003	76.54703876546589
2004	75.19713564763006
2005	75.74513788756299
2006	74.56307191429713
2007	74.73558378888558
2008	75.07600268385188
2009	75.06600051299618
2010	75.38539269213045
2011	74.69174697991518
2012	74.43947914516627
2013	73.17351572373609
2014	73.19287431821834
2015	74.089062024806