Annual % of total
1960 94.42732405571995
1961 94.38922762388808
1962 94.49635620581748
1963 94.6816493649933
1964 94.78318705767028
1965 94.75366354012002
1966 94.65255590180705
1967 94.77874309678418
1968 94.76749367737537
1969 94.82589127039475
1970 94.71625840924143
1971 94.59207220671425
1972 94.27028438817831
1973 94.27621569133161
1974 93.61861856484967
1975 92.86413208520877
1976 92.90738705335617
1977 92.26092097264099
1978 91.65622437320239
1979 91.61144630688501
1980 91.02013873136389
1981 89.95916702517862
1982 89.16645245294627
1983 88.23645019722
1984 87.22276452475093
1985 86.07552586894495
1986 85.50313364060924
1987 85.15412721508882
1988 84.94219184925356
1989 84.8351278878303
1990 84.04462250814238
1991 83.45292391889177
1992 83.46183854626418
1993 83.31899572870513
1994 83.2717908568728
1995 83.00460822111295
1996 82.99403193537599
1997 83.25729921691885
1998 83.01211336244994
1999 82.88799045185725
2000 82.8941901533154
2001 83.23449279792095
2002 83.11799950782856
2003 83.43057874333095
2004 83.02436662236325
2005 82.71954214104446
2006 82.49553564982743
2007 82.85907776734973
2008 82.37333306483569
2009 81.49274897597014
2010 81.18542782385751
2011 81.74849146159845
2012 81.68459575460541
2013 81.45997169743215
2014 81.1078736432346
2015 79.0819006212285