Annual % of total
1960 12.828947368421053
1961 14.061838204150783
1962 16.416129801956576
1963 18.90451832907076
1964 22.003593121738383
1965 23.56107988282796
1966 25.392886683209266
1967 27.539218293007178
1968 29.520113349350087
1969 33.93735152753992
1970 41.532934131736525
1971 46.07927003136584
1972 46.85508451094486
1973 47.65304491448666
1974 49.277003036072664
1975 46.85806063039551
1976 48.29229148904158
1977 48.73292465125259
1978 48.67348317643349
1979 45.21658559184618
1980 39.9555155932043
1981 40.534002738475586
1982 43.75279710321819
1983 43.47279146207848
1984 41.23819517313746
1985 41.10901793758702
1986 41.738782051282044
1987 39.61342990916003
1988 39.31272055116787
1989 39.91713875031707
1990 34.0927311038608
1991 29.074473639310693
1992 26.30688372936695
1993 48.07215017064846
1994 29.934833707025412
1995 32.4256939111355
1996 26.833169269887396
1997 21.973142214727375
1998 24.122901759240957
1999 25.72694356659142
2000 24.339469189937688
2001 22.853239497618016
2002 27.37432729773092
2003 25.146017957820003
2004 24.133181432810513
2005 27.00468253968254
2006 27.152423933020213
2007 24.23063283922463
2008 24.231665000999403
2009 26.9670002327205
2010 24.87182608695652
2011 20.834052748137708
2012 24.21097739361702
2013 25.131197890507284
2014 26.084934880416768
2015 26.47066905347953
2016 29.27274556780067