Year	% of total
1970	2.1836525817993455
1971	2.294016609934888
1972	2.221889037438218
1973	2.300636319526071
1974	2.4263927920014954
1975	2.339339018129745
1976	2.34269228034188
1977	2.445448039733151
1978	2.509682795273559
1979	2.6453917398230686
1980	2.701636898432408
1981	2.769916639473661
1982	2.7799784602618316
1983	2.7435847411063916
1984	2.781530777962106
1985	3.2226541865692613
1986	2.65025544395199
1987	2.6045120874591
1988	2.6951212225824106
1989	2.4851137042439397
1990	1.7178259645170373
1991	1.8089315997738835
1992	1.8836565096952906
1993	1.9932622122403143
1994	2.0202020202020203
1995	2.178649237472767
1996	2.296056185845489
1997	2.4325046778936112
1998	2.537796976241901
1999	2.6259378349410505
2000	2.5602027883396707
2001	2.543881963876876
2002	2.481825018801705
2003	2.237953870746746
2004	2.205547976352888
2005	2.2048690858980247
2006	2.247941241931894
2007	2.260245035910435
2008	2.4363715466608658