Year	% of total
1970	1.1487266836163748
1971	2.510788273615635
1972	2.285352494346929
1973	2.1054231239424532
1974	2.5771554591432455
1975	2.0392869206568447
1976	2.462669559176111
1977	2.2430839356388197
1978	2.140277136942776
1979	1.5411468439370037
1980	2.0810406310784524
1981	2.5642017695444808
1982	2.2857194461089114
1983	2.357823281703455
1984	3.4287653794128294
1985	3.79642468286838
1986	4.125036275628316
1987	2.558145055581951
1988	4.462936700977627
1989	3.688272487228058
1990	4.273504273504273
1991	4.693140794223827
1992	5.225653206650831
1993	5.607476635514018
1994	6.105990783410138
1995	6.164383561643835
1996	6.286379511059372
1997	6.940874035989718
1998	6.115515288788222
1999	6.555423122765197
2000	7.051282051282051
2001	6.772009029345373
2002	6.743940990516332
2003	7.142857142857142
2004	7.931404072883172
2005	7.884231536926148
2006	8.677248677248677
2007	8.483033932135728
2008	8.178438661710038