Year	% of total
1970	4.584676607812643
1971	4.6157288036270545
1972	4.978852900907068
1973	5.00415415029911
1974	5.229909942267273
1975	5.194095988882901
1976	5.291307642145141
1977	5.301368643972333
1978	5.369913563865221
1979	5.637271547142039
1980	5.430332691724237
1981	5.727510258390027
1982	5.901933280997286
1983	5.6588633195048965
1984	6.130875370789672
1985	6.047782703940979
1986	5.97620295999285
1987	5.690550782997763
1988	6.0588220168969515
1989	6.486341502830024
1990	50
1991	6.043956043956044
1992	3.4682080924855487
1993	2.357563850687623
1994	1.9287833827893175
1995	1.6706443914081146
1996	1.7462165308498252
1997	1.8181818181818181
1998	1.7738359201773837
1999	1.83982683982684
2000	2.6260504201680672
2001	2.823018458197611
2002	3.0303030303030303
2003	3.1286210892236386
2004	3.357314148681055
2005	3.61145703611457
2006	3.841229193341869
2007	4.095112285336857
2008	4.217687074829931