Year	% of total
1990	74.76114025382586
1991	74.55263246958786
1992	75.22767523557555
1993	75.03839264975306
1994	74.19339440874806
1995	72.48098106636664
1996	71.36351130724293
1997	69.87426899683169
1998	69.17378557812555
1999	67.45290097607146
2000	64.1032143524436
2001	64.54880047804133
2002	64.92502215396459
2003	64.23531800451956
2004	65.25689305514959
2005	65.20727547851301
2006	64.86038834434142
2007	63.33034338015629
2008	61.71189720157011