Annual % of total
1960 29.116390616802818
1961 31.233775105888782
1962 36.4230323013983
1963 34.760925129356025
1964 42.846569883290634
1965 44.68392286274106
1966 51.13459451809218
1967 55.04789353225396
1968 58.595961502170226
1969 57.59273277819833
1970 61.60190673315144
1971 65.39097230137924
1972 67.17742547219905
1973 68.80738275626048
1974 71.15779664965373
1975 69.31664479660846
1976 71.51304604922758
1977 68.60826867573748
1978 72.85048010973937
1979 70.74079406788812
1980 68.72185837085551
1981 63.55080667987545
1982 59.08249187659411
1983 56.202119281162744
1984 56.247350474610634
1985 54.02081017548335
1986 52.39791301669202
1987 54.16786736595394
1988 59.11712143265103
1989 56.139385899634384
1990 55.5831383127151
1991 55.75833490841997
1992 55.893042412250516
1993 57.04521113199762
1994 58.83315153637398
1995 57.47730609360712
1996 60.49832855280314
1997 57.40261413458831
1998 59.03953009132776
1999 57.11512917250548
2000 54.8455978316457
2001 56.676228501645234
2002 53.725214068745
2003 54.475652105692596
2004 53.43246066277268
2005 51.89772753209701
2006 53.105945052372874
2007 51.48770722905154
2008 53.84775018509378
2009 56.305395318098014
2010 56.90996120768528
2011 53.146108965014584
2012 49.4276246889739
2013 52.97667174629325
2014 53.55165297144754
2015 53.292264320274704
2016 56.7722199732826