Annual % of total
1960 5.6351480420248325
1961 6.675102815564695
1962 10.380952380952381
1963 15.086483023702755
1964 16.895113230035758
1965 20.3125
1966 24.39255285579047
1967 27.630729502905105
1968 28.212791392707715
1969 28.932740411339637
1970 29.714590557481994
1971 31.861111111111107
1972 32.58152173913044
1973 34.54968944099379
1974 30
1975 32.693498452012385
1976 35.18117064106534
1977 37.88590604026845
1978 35.28319405756732
1979 31.185722928009678
1980 27.003658131027603
1981 30.493971217425127
1982 32.20198675496689
1983 32.950022114108805
1984 29.938398357289525
1985 31.56
1986 35.12413512413512
1987 41.53976311336717
1988 41.190965092402465
1989 42.255125284738035
1990 38.937579505300356
1991 44.10983870967742
1992 46.909441535776615
1993 46.12815766923736
1994 48.746743542435425
1995 54.58253456221198
1996 55.50732876712329
1997 60.21506650544135
1998 67.63899868247695
1999 67.75877987421384
2000 68.21132867132867
2001 67.92375273522975
2002 63.98616869918698
2003 66.58500000000001
2004 66.62135273972602
2005 68.18040201005024
2006 65.46875638841567
2007 67.54653500897666
2008 68.62338768115941
2009 67.4854206500956
2010 66.94098553345388
2011 70.42116193961574
2012 69.84108512628625
2013 72.40066995073892
2014 72.58
2015 74.06295728368018
2016 74.62303611738147