Year	% of total
1970	4.185600256090809
1971	4.004815772409321
1972	3.976104889244927
1973	4.06017629992179
1974	3.8157354301135022
1975	3.7201685929071755
1976	3.7369539903900137
1977	3.7183260664559077
1978	3.9410195500952234
1979	4.0215090006323635
1980	3.943960267465406
1981	4.031865435356751
1982	5.039486583418851
1983	5.452502042793431
1984	5.68993017803601
1985	6.33922364465834
1986	6.935224616976192
1987	6.860815797553285
1988	7.579336518156714
1989	7.970661375754222
1990	6.790123456790123
1991	7.453416149068323
1992	7.83132530120482
1993	8.284023668639055
1994	8.571428571428571
1995	8.98876404494382
1996	8.947368421052632
1997	9.375
1998	9.644670050761421
1999	10.471204188481675
2000	10.606060606060606
2001	10.552763819095476
2002	10.714285714285714
2003	10.83743842364532
2004	9.95260663507109
2005	10
2006	10
2007	9.734513274336283
2008	9.90566037735849