Year	% of total
1970	4.705240135421074
1971	4.476267583272942
1972	4.566245864203471
1973	4.571325770839648
1974	4.533054168819932
1975	5.841166841490532
1976	6.145248991236667
1977	6.200718479628561
1978	6.497500576779312
1979	6.720772864595672
1980	6.94369763248337
1981	6.965604389808323
1982	6.960456072876736
1983	6.854855267982314
1984	6.845720049204456
1985	6.952313644144435
1986	6.880905351916303
1987	6.829307318895483
1988	7.222165060806816
1989	7.327717303830859
1990	4.720320981826765
1991	4.366590505204367
1992	4.165493948775683
1993	4.07573812580231
1994	3.854166666666667
1995	3.779406093328191
1996	3.58883473637572
1997	3.4794396746497966
1998	3.8304392236976508
1999	3.902439024390244
2000	3.827227993439038
2001	4.017139796464917
2002	4.128440366972478
2003	4.565217391304348
2004	4.623955431754875
2005	4.769921436588103
2006	5.138121546961326
2007	5.015673981191222
2008	4.519230769230769