Year	% of total
1960	100
1961	100
1962	100
1963	100
1964	97.82608695652173
1965	93.07359307359307
1966	94.0959409594096
1967	93.72384937238493
1968	93.63957597173145
1969	92.97124600638978
1970	92.66862170087977
1971	93.04556354916068
1972	92.51559251559252
1973	93.36917562724015
1974	92.3076923076923
1975	91.90647482014388
1976	91.3884007029877
1977	92.28611500701263
1978	91.59347553324967
1979	90.55118110236221
1980	88.83928571428571
1981	89.73941368078177
1982	89.80667838312829
1983	90.94076655052264
1984	88.27838827838828
1985	89.48220064724919
1986	89.45147679324894
1987	89.49468085106383
1988	90.52369077306733
1989	89.76572133168928
1990	92.24996515679442
1991	97.66683006535948
1992	82.97139759036145
1993	84.3059090909091
1994	98.97119587628866
1995	92.17054054054054
1996	95.6819867549669
1997	100.61790645879731
1998	95.1082470119522
1999	98.65976190476191
2000	100.00909090909092
2001	93.09579335793359
2002	100.11175724637683
2003	97.99741379310345
2004	98.89787878787878
2005	91.58727272727273
2006	95.36435975609756
2007	87.86325000000001
2008	90.26086436170213
2009	91.67500000000001
2010	94.2795499296765
2011	85.33301480484523
2012	85.1531543624161
2013	85.9246915167095
2014	86.68731800766284
2015	85.40122015915121
2016	85.7297400990099