Year	% of total
1970	2.398962670319371
1971	2.8752347531629354
1972	2.642411168734282
1973	3.0606436983784597
1974	2.8943654757467656
1975	2.715149453163828
1976	2.4794449215262016
1977	2.776580821431599
1978	2.595608968292401
1979	2.64776447124544
1980	2.544511185079608
1981	2.642952362416568
1982	2.5934175928738634
1983	2.6889526208829406
1984	3.03992681971473
1985	3.087485635058046
1986	2.9568595658223087
1987	2.6860624297230093
1988	2.95352113365112
1989	2.8891968555573198
1990	3.9497138568345997
1991	4.762758991837833
1992	4.610619469026549
1993	4.49438202247191
1994	4.436974789915967
1995	3.7422903817302884
1996	4.696035242290749
1997	4.696203616419573
1998	4.4390637610976595
1999	4.451779101593946
2000	4.549473514990757
2001	4.354504262345442
2002	4.260312944523471
2003	4.336228712126394
2004	4.280155642023346
2005	4.7616
2006	5.082221934481419
2007	5.168426973314168
2008	5.654974946313529