Year	% of total
1970	4.707765094128464
1971	4.3998756877999705
1972	4.31495103380342
1973	4.257749634148437
1974	4.202960549074339
1975	4.291731155430652
1976	4.38257848520993
1977	4.496191280319312
1978	4.786166960751942
1979	5.317397346619289
1980	5.259025675584608
1981	5.432726823643195
1982	5.556598854792232
1983	5.823289980575038
1984	5.582460693813183
1985	5.672092451451592
1986	5.861143932383577
1987	5.7002984888417565
1988	6.075011130237056
1989	6.0088023401871995
1990	4.166666666666666
1991	4.186046511627907
1992	4.205607476635514
1993	4.090909090909091
1994	4.186046511627907
1995	5.092592592592593
1996	4.961832061068702
1997	5.928853754940711
1998	6.071428571428571
1999	6.418918918918918
2000	6.862745098039216
2001	6.9306930693069315
2002	7.094594594594595
2003	6.862745098039216
2004	6.666666666666667
2005	6.521739130434782
2006	6.832298136645963
2007	6.567164179104477
2008	6.769230769230769