Year	% of total
1970	11.60928929556856
1971	11.587497316459917
1972	12.744591104708025
1973	12.578309971133677
1974	13.009703521138452
1975	12.942385239955309
1976	13.230603260333973
1977	13.068265628670666
1978	12.921103327626875
1979	12.17505996937548
1980	12.0613874004639
1981	12.049703529060828
1982	12.588325224845773
1983	13.312917566547533
1984	13.872063111826977
1985	16.09432928119528
1986	16.70138563268407
1987	17.207270681589
1988	17.48678435631986
1989	18.225600977764785
1990	19.958148051268637
1991	20.145631067961165
1992	19.973509933774835
1993	19.622440840202074
1994	18.90359168241966
1995	19.11963273021874
1996	19.079837618403246
1997	20.06892895015907
1998	20.751677852348994
1999	22.338751966439432
2000	22.88659793814433
2001	21.707060063224446
2002	20.9962506695233
2003	20.809716599190285
2004	20.570813139472264
2005	21.486100285788517
2006	21.654135338345863
2007	24.982290436835893
2008	27.662957074721778