Annual % of total
1960 71.01190476190476
1961 71.16082224909312
1962 73.02716688227684
1963 76.0810810810811
1964 66.96950032446463
1965 63.36853807670928
1966 70.90039147455414
1967 72.24152910512598
1968 72.15702144880616
1969 69.85365853658537
1970 45.39041595718803
1971 40.836770771950505
1972 25.624110723062994
1973 24.4927258805513
1974 30.134467302608897
1975 35.283342873497425
1976 28.196966860138552
1977 33.13200280112045
1978 21.07084212995543
1979 33.69504059159232
1980 28.0154355016538
1981 39.126658243840815
1982 47.51143897656177
1983 41.87861473068079
1984 32.04744713769985
1985 30.94362436394781
1986 29.86394884861304
1987 29.851787271142115
1988 32.52959419910017
1989 31.448989875853222
1990 34.206968625718076
1991 38.97077681505826
1992 43.382117593712216
1993 38.13240778549068
1994 42.59460097833683
1995 37.101707049965775
1996 38.41081081081081
1997 41.25186187010847
1998 44.428061443520264
1999 28.639865875677067
2000 39.30628324214277
2001 38.092268289420886
2002 36.71104340256186
2003 38.1308516221374
2004 38.69162327718224
2005 34.922828407686254
2006 37.61266346666667
2007 38.15474830879427
2008 35.957687277622846
2009 39.840457568502266
2010 40.128272052324554
2011 39.749112916878275
2012 38.36103600758054
2013 39.997990916788545
2014 38.109748577191844
2015 38.06424881825032
2016 37.33509940704569