Year	% of total
1970	15.177928217928615
1971	14.697065109200267
1972	14.785539653714363
1973	14.786208275610466
1974	14.640564245362006
1975	15.710675644942187
1976	15.976413718232486
1977	16.148683136830122
1978	16.0641201209147
1979	16.252902400592056
1980	11.389771814794802
1981	11.440193690321895
1982	11.320499119944538
1983	11.1460007678567
1984	10.870761702854972
1985	10.745414873063934
1986	11.10728382982684
1987	11.057733290516541
1988	11.348422564993218
1989	11.747733240299649
1990	6.417112299465241
1991	6.25
1992	5.228758169934641
1993	5.0359712230215825
1994	5.6000000000000005
1995	6.666666666666667
1996	7.758620689655173
1997	7.82608695652174
1998	6.779661016949152
1999	6.896551724137931
2000	6.779661016949152
2001	8.547008547008547
2002	9.401709401709402
2003	7.627118644067797
2004	7.43801652892562
2005	8.403361344537815
2006	7.563025210084033
2007	7.317073170731707
2008	6.976744186046512