Year	% of total
1970	1.867163748410447
1971	1.861753266349999
1972	1.8013093507582993
1973	1.7001568428411367
1974	1.915885816996727
1975	1.615519145171047
1976	1.634454824305433
1977	1.6414993740758166
1978	1.5848828551015048
1979	1.7497150462279933
1980	1.6687203513378546
1981	1.6973935176350696
1982	1.6641181545719665
1983	1.5817835974057959
1984	1.484658783705634
1985	1.6732761656418758
1986	2.585531705388338
1987	2.6218286298095457
1988	2.7303630608112504
1989	2.7220591427021166
1990	2.576808721506442
1991	2.644964394710071
1992	2.7245206861755804
1993	2.8265107212475633
1994	3.145853193517636
1995	3.6121673003802277
1996	4.310344827586207
1997	4.910292728989613
1998	5.324909747292419
1999	3.4227567067530065
2000	3.6414565826330536
2001	3.9159503342884436
2002	3.896103896103896
2003	4.12573673870334
2004	4.166666666666666
2005	4.37956204379562
2006	4.463336875664187
2007	4.442036836403034
2008	4.461371055495103