Annual % of total
1960 91.0689812699863
1961 89.39914163090128
1962 90.19917176099389
1963 90.91527730520585
1964 89.92816091954023
1965 91.5892809763863
1966 92.47653230259525
1967 86.84308609765189
1968 87.64008965738073
1969 76.68962949171477
1970 76.56408522150828
1971 80.33412887828162
1972 83.58487853960041
1973 81.70750500847589
1974 77.63896687254352
1975 74.40160358448296
1976 77.96321887955779
1977 78.16192136354832
1978 79.24633896091781
1979 77.1516393442623
1980 85.62049120531734
1981 83.62825492734859
1982 83.22953159465422
1983 83.87821953882715
1984 82.99155609167673
1985 81.18261069052537
1986 80.40719976394216
1987 76.90309298563795
1988 74.50922509225093
1989 70.38711643974803
1990 60.02695692236812
1991 58.042715068799644
1992 57.611231852654385
1993 68.39635848851138
1994 61.477299548767796
1995 63.297361489060634
1996 55.48814818642141
1997 67.75625529049634
1998 75.64886428113846
1999 69.41940873811808
2000 75.65989898989899
2001 53.18484681225502
2002 44.76243228432754
2003 55.89352941176471
2004 53.050585885486015
2005 49.36600846877141
2006 49.52282090699462
2007 46.55236678922241
2008 48.90108925549916
2009 50.53965982914727
2010 48.006908396946564
2011 50.131369475720454
2012 46.033875523751234
2013 46.23525352848928
2014 54.748572351719375
2015 49.61932197388803
2016 49.1007475636861