Year	% of total
1970	13.00603830084186
1971	12.582088651541776
1972	12.023971639204397
1973	12.24783525442199
1974	11.24593716122419
1975	11.48810693554993
1976	10.460038952933107
1977	10.266862082989794
1978	10.35426384757167
1979	10.63240046463453
1980	10.74335273463274
1981	11.155446260593745
1982	11.270687886062118
1983	10.991181215149922
1984	10.769239606208494
1985	10.369617835508524
1986	10.969487334849012
1987	11.016659144766287
1988	9.495443726274374
1989	9.337748197784128
1990	16.412446613788894
1991	14.778645833333334
1992	16.734143049932523
1993	18.34319526627219
1994	19.522591645353792
1995	19.633943427620633
1996	19.453642384105958
1997	18.110918544194107
1998	17.013574660633484
1999	14.647887323943662
2000	15.704824976348156
2001	15.562248995983936
2002	16.96712619300106
2003	17.497456765005087
2004	14.070891514500536
2005	15.315315315315313
2006	14.840989399293287
2007	16.33605600933489
2008	17.12907117008444