Annual % of total
1960 77.89855072463769
1961 79.74276527331192
1962 79.46428571428571
1963 79.22535211267605
1964 76.18181818181819
1965 74.70489038785834
1966 74.42528735632185
1967 71.54582763337892
1968 71.12171837708831
1969 68.47457627118645
1970 66.307541625857
1971 67.56529064869419
1972 72.3846653671215
1973 66.11226611226611
1974 55.780590717299575
1975 53.47166799680766
1976 53.629629629629626
1977 51.53846153846153
1978 50.59288537549408
1979 49.78250362493959
1980 30.425531914893618
1981 47.65234765234766
1982 43.05067737079779
1983 41.03796251802018
1984 37.67572633552015
1985 34.993020009306655
1986 35.639508420573506
1987 37.93103448275862
1988 35.18518518518518
1989 45.632653061224495
1990 35.942661157024794
1991 54.24661800486618
1992 63.19026785714286
1993 71.56850241545895
1994 75.05355140186916
1995 91.0168205128205
1996 89.16208121827411
1997 95.39155405405407
1998 90.45266666666666
1999 93.95915824915825
2000 89.766309148265
2001 97.14133540372671
2002 97.10216
2003 94.75313868613138
2004 87.70027972027972
2005 96.22496314496316
2006 87.55528395061728
2007 80.1178672985782
2008 91.10340527577938
2009 79.11212962962962
2010 76.30242358078603
2011 74.9406746031746
2012 68.93639737991266
2013 69.5887891440501
2014 73.97224137931035
2015 65.89027613412229
2016 68.20768762677486