Year	% of total
1970	14.85815666691303
1971	15.770419425171053
1972	15.61108449038256
1973	17.06331757616149
1974	17.01763730235454
1975	17.123430064975597
1976	16.63413544394449
1977	15.844386362259891
1978	15.680050476443725
1979	15.523496447973656
1980	15.305050042880012
1981	16.11962229780516
1982	17.392810841207876
1983	18.189306526319648
1984	18.30093330750651
1985	17.808398585335798
1986	14.958391269836374
1987	14.625253584037315
1988	12.539872556017784
1989	12.322556143327313
1990	16.091954022988507
1991	16.991643454038996
1992	17.934782608695652
1993	19.398907103825135
1994	19.895287958115183
1995	20.491803278688526
1996	18.434343434343432
1997	18.75
1998	18.817204301075268
1999	17.435897435897434
2000	17.539267015706805
2001	15.571776155717762
2002	14.452214452214452
2003	14.150943396226415
2004	13.488372093023257
2005	12.903225806451612
2006	12.584269662921349
2007	12.280701754385964
2008	12.121212121212121