Annual % of total
1960 8.005181347150259
1961 9.382036527395547
1962 10.541894353369763
1963 11.487423252129135
1964 14.04353689077249
1965 15.843583624013219
1966 17.58975284142161
1967 19.326874043855177
1968 18.9149125407649
1969 24.025676295277396
1970 19.376224197679672
1971 21.436516764659146
1972 20.37617554858934
1973 25.120772946859905
1974 29.661683713611332
1975 19.804216867469883
1976 25.34562211981567
1977 27.19242902208202
1978 27.84887263863498
1979 28.847214561500273
1980 29.044647143542967
1981 30.79056865464633
1982 36.84434968017058
1983 42.78717720391808
1984 48.99517684887461
1985 49.7312791114296
1986 50.063979526551506
1987 50.015455950540954
1988 51.70546832701679
1989 55.164895066775685
1990 65.82774305555556
1991 83.70105263157896
1992 81.34411167512691
1993 82.73358790771678
1994 84.79598966026587
1995 78.79064652567976
1996 80.31645659928655
1997 69.97648919346337
1998 74.4639116883117
1999 77.71633018398806
2000 78.03172748267897
2001 73.3826726144298
2002 72.56462267590229
2003 74.77452322738387
2004 75.69418277104488
2005 75.64939162335678
2006 78.77410584958217
2007 77.92495656751777
2008 77.56436988936989
2009 79.26456089385475
2010 77.95818703044681
2011 72.87505512679162
2012 71.99309363683393
2013 71.59063882469461
2014 72.05252664576804
2015 68.04589343004604
2016 72.67860726878222