Year	% of total
1970	1.9547953670565479
1971	1.7736788895927946
1972	1.4319266140435187
1973	1.2200562623510132
1974	1.3364684390330366
1975	1.7971041384108366
1976	1.5496194524700528
1977	1.5254213132550274
1978	1.8988722397511957
1979	1.9011318531827932
1980	1.7503385124570054
1981	2.042642935129255
1982	2.9657368385695424
1983	4.131874040939524
1984	6.514448796723587
1985	7.559854556845884
1986	6.65402797047097
1987	6.819472620924946
1988	5.668252701585348
1989	5.447390644298139
1990	10.358974358974358
1991	10.00478697941599
1992	9.78017048003589
1993	9.509721048182588
1994	9.301397205588822
1995	8.94278135657446
1996	8.61882437793004
1997	8.261617900172118
1998	7.6923076923076925
1999	6.961220597584234
2000	6.938527084601338
2001	6.820843091334895
2002	6.632797064634491
2003	6.4577656675749315
2004	6.6876475216365066
2005	6.61764705882353
2006	6.157635467980295
2007	6.039627596084984
2008	5.291375291375291