Year	% of total
1970	17.242034578280034
1971	15.767942295462396
1972	11.565812275919093
1973	9.099723211291662
1974	10.896820301178213
1975	12.617553371071999
1976	10.213654084934047
1977	10.456262666565369
1978	10.217314582162638
1979	11.2594273037634
1980	12.596147685845432
1981	14.149106162754293
1982	15.223560908519417
1983	14.366860173688758
1984	12.948568735185667
1985	11.175801976368632
1986	11.092123261540674
1987	11.399251055242155
1988	11.304879562677067
1989	11.04420156617276
1990	19.755323969188947
1991	18.896925858951175
1992	19.387755102040817
1993	19.474835886214443
1994	18.646288209606986
1995	16.673159329957148
1996	15.1493848857645
1997	13.782051282051283
1998	13.282621416032766
1999	12.78600269179004
2000	11.923847695390782
2001	11.527377521613833
2002	10.77386468952734
2003	10.666666666666668
2004	10.705907442951588
2005	10.388808887060277
2006	10.698824984539272
2007	10.93427035965275
2008	10.85916371957562