Annual % of total
1960 6.167873696041231
1961 7.76585116801956
1962 9.206612034126628
1963 10.521288566718132
1964 12.038140154816219
1965 13.143422682963132
1966 13.804477147511577
1967 14.455711757508286
1968 15.243164276994273
1969 15.664712950928223
1970 13.796351563082892
1971 14.710792698643296
1972 14.704429281381207
1973 14.91417082528977
1974 15.230327702329122
1975 15.812936389419882
1976 16.750903802447038
1977 17.37919379781402
1978 17.629625715311125
1979 18.617760575605548
1980 18.697932477529097
1981 20.463842967464394
1982 21.269162105448977
1983 22.53352753370364
1984 24.203758878209143
1985 24.643604103776774
1986 23.7405488951084
1987 27.47101709664844
1988 28.58255458942938
1989 29.363314013927056
1990 53.92202668058591
1991 54.809099709538536
1992 41.60485167769506
1993 44.75785463747194
1994 46.53100082461699
1995 46.3414225190108
1996 47.51460557358673
1997 50.00400817064454
1998 50.20820487694835
1999 49.476484084744015
2000 49.05212588116818
2001 49.98631761856521
2002 50.000031239106534
2003 51.54864550417491
2004 51.75395920788465
2005 52.314605088676224
2006 51.66741171883352
2007 52.68004674805689
2008 52.0036857309347
2009 53.674116187456946
2010 55.48654911695596
2011 54.57690602847549
2012 53.19158549608245
2013 54.46331128926983
2014 54.93516802957321
2015 53.56283140613664
2016 55.54778019465674