Year	% of total
1970	19.00540954377862
1971	30.75799391419916
1972	28.981242527965417
1973	34.22660496854714
1974	40.62459221973194
1975	32.39001636213799
1976	34.99905065421661
1977	27.757953141678527
1978	26.474956661670028
1979	21.50349302951656
1980	25.91385283137504
1981	29.536340841421698
1982	27.392869283655457
1983	28.12274548136778
1984	34.533235469861566
1985	33.75500059006388
1986	34.26367469213426
1987	27.128456217710045
1988	34.83027597122835
1989	32.21974251670112
1990	24.571428571428573
1991	22.54335260115607
1992	21.052631578947366
1993	19.526627218934912
1994	17.46987951807229
1995	18.93491124260355
1996	30.701754385964914
1997	30.833333333333336
1998	32
1999	33.33333333333333
2000	37.39837398373984
2001	36.09022556390977
2002	31.67701863354037
2003	26.21359223300971
2004	25.688073394495415
2005	24.18032786885246
2006	26.81992337164751
2007	30.916030534351147
2008	33.81818181818182