Annual % of total
1960 80.67940552016985
1961 82.15767634854772
1962 83.87755102040816
1963 84.9340866290019
1964 87.2340425531915
1965 84.52380952380952
1966 83.73570520965691
1967 80.16627078384798
1968 83.5881753312946
1969 83.36501901140684
1970 82.66405484818804
1971 87.11923411662316
1972 84.13312693498452
1973 82.76385725132877
1974 78.19293478260869
1975 79.70918704560475
1976 82.19435736677116
1977 83.4508952794357
1978 81.00832109642683
1979 78.80434782608697
1980 78.21552723059096
1981 76.95749440715883
1982 77.9445727482679
1983 76.45150827116444
1984 70.53032708796444
1985 66.76904176904176
1986 72.79635258358662
1987 61.48564294631711
1988 67.8729037952339
1989 61.37434192297035
1990 64.05915636363636
1991 78.06997226074897
1992 65.5856719367589
1993 68.63416464891041
1994 58.16544744744745
1995 52.87452464788732
1996 56.77599431818182
1997 54.48056655665566
1998 55.1406712473573
1999 51.9922933467742
2000 53.62965599617774
2001 53.21807852193995
2002 52.7015232397607
2003 53.3534247828075
2004 53.31043802014892
2005 53.24598098530683
2006 51.24963855421687
2007 49.890342577487765
2008 48.32629689390883
2009 46.08230769230769
2010 41.935298833819246
2011 41.91671850699844
2012 40.600892053973006
2013 42.57391109450877
2014 41.1472251127298
2015 45.77879339400067
2016 45.511783373577096