Year	% of total
1970	1.1261803466771594
1971	2.0602735548963502
1972	1.9174554000557311
1973	1.7997140251109094
1974	2.0852248993035674
1975	1.7663858692228436
1976	1.9963174600314837
1977	1.7707435321023934
1978	1.7105066552358712
1979	1.3270078449495242
1980	1.6197465787779168
1981	1.8872511865314003
1982	1.7022737307144737
1983	1.7497020371318803
1984	2.337253686503945
1985	2.32262290168258
1986	2.442384741942754
1987	1.7976321217144982
1988	2.549166801156458
1989	2.2791435810025256
1990	6.019070321811681
1991	6.0248080330773774
1992	6.0375146541617815
1993	6.0606060606060606
1994	6.104651162790697
1995	5.516111414527581
1996	5.878962536023055
1997	6.0046189376443415
1998	5.620985010706638
1999	5.602094240837696
2000	6.087936865839909
2001	6.844106463878327
2002	7.1569595261599215
2003	7.309417040358744
2004	8.257299270072993
2005	8.665511265164644
2006	9.563602599814299
2007	9.18942349371478
2008	9.399141630901289