Year	% of total
1970	9.374377176071397
1971	9.12339828233622
1972	9.19451650521426
1973	9.360870473232241
1974	9.476665431495872
1975	9.455954691017313
1976	9.590050884408438
1977	9.611813554039289
1978	9.312400415332002
1979	9.018273955122867
1980	8.696836514403019
1981	8.405492276137274
1982	8.352911717967777
1983	8.22966054882068
1984	8.10135308955043
1985	8.187271100485933
1986	8.377348190475283
1987	8.32087779198142
1988	13.520668015746734
1989	15.380445664314854
1990	22.177419354838708
1991	22.131147540983605
1992	23.340961098398168
1993	23.902439024390244
1994	15.342465753424658
1995	12.316715542521994
1996	7.9113924050632916
1997	8.30670926517572
1998	5.743243243243244
1999	7.719298245614035
2000	9.059233449477352
2001	9.830508474576272
2002	8.389261744966444
2003	9.235668789808917
2004	7.120743034055728
2005	6.997084548104956
2006	5.88235294117647
2007	4.644808743169399
2008	3.4229828850855744