Year	% of total
1970	3.806156519111649
1971	4.479119326663083
1972	4.191295070081679
1973	4.825929485844519
1974	5.037840682736835
1975	5.535324614408598
1976	6.2959332074009
1977	5.318408828234077
1978	5.578782295428679
1979	6.042846416329197
1980	5.630478505826965
1981	5.007040598095308
1982	5.581968658963554
1983	5.58670927727244
1984	5.673649508485143
1985	5.999823298641506
1986	6.171402986953717
1987	5.716436238729068
1988	5.015883149392036
1989	5.318449581716941
1990	12.410501193317423
1991	18.243243243243242
1992	15.909090909090908
1993	12.97539149888143
1994	13.729977116704806
1995	15.085158150851582
1996	15.422885572139302
1997	14.761904761904763
1998	14.220183486238533
1999	14.553990610328638
2000	14.588235294117647
2001	11.205432937181664
2002	11.129032258064516
2003	23.10126582278481
2004	21.839080459770116
2005	19.753086419753085
2006	20.398009950248756
2007	21.464646464646464
2008	20.276497695852534