Year	% of total
1970	50.438569280521506
1971	51.984543474565555
1972	50.84909395660024
1973	54.45137174732879
1974	53.92765418655504
1975	54.489953346511165
1976	54.67599597008116
1977	54.210182287568685
1978	55.21120349802988
1979	54.349949727411285
1980	53.992619483443235
1981	52.122917578143124
1982	54.34829457191326
1983	52.14682016243305
1984	53.45978939300189
1985	52.1469715901683
1986	53.30868552201895
1987	52.27259060199964
1988	55.210397830711536
1989	53.3438833344972
1990	65.00146070698219
1991	64.61852067559697
1992	63.250071777203566
1993	62.38745280278827
1994	61.89383070301291
1995	61.84807256235828
1996	61.79401993355482
1997	62.35791699709225
1998	62.447807933194156
1999	62.26269881990765
2000	62.33308138070043
2001	62.231016571852585
2002	62.209159931422974
2003	62.42069302098585
2004	63.15660284732449
2005	62.35816477553035
2006	61.720698254364095
2007	61.854661120626375
2008	60.2287166454892