Annual % of total
1960 2.995759678396387
1961 3.3587894215811063
1962 3.9424280350438052
1963 4.066355821993847
1964 4.621557211378925
1965 5.467382598119197
1966 5.8499985487475685
1967 6.224277652849082
1968 7.051775894588635
1969 7.045454545454547
1970 8.4555900845559
1971 8.729499081043747
1972 9.111014792340434
1973 10.30732138376444
1974 10.57360931983001
1975 11.05003124511795
1976 11.39057876454263
1977 11.843107054406707
1978 12.197957953879973
1979 12.628037259256805
1980 12.117672131406335
1981 11.891795215738878
1982 10.998106619882227
1983 10.632700372483136
1984 9.297353030661574
1985 9.237816411454137
1986 9.397015408258179
1987 9.054159476135316
1988 8.908147575625518
1989 9.31745811989478
1990 9.752280852035863
1991 9.789303813667775
1992 10.614297405131492
1993 10.901229288994827
1994 11.696623693892569
1995 12.466721470588237
1996 13.115005065856128
1997 13.860181063749527
1998 15.372355139599888
1999 16.36015114246877
2000 16.830179567819822
2001 17.899106607629427
2002 18.1448082010582
2003 17.780700369499495
2004 18.797900735537738
2005 18.920916874066698
2006 19.030246107803496
2007 19.543213134633184
2008 20.768407498702647
2009 20.995875664401535
2010 20.923896857270353
2011 21.400573746740076
2012 21.003502554804683
2013 19.109995307210138
2014 19.622184503394692
2015 20.294412385400452
2016 22.103052312003733