Year	% of total
1990	67.06095882096066
1991	65.89192940699238
1992	65.27145647680719
1993	64.50504753383261
1994	62.960122753044274
1995	63.273449004801364
1996	63.95031176562971
1997	64.59872741577847
1998	65.29898453732918
1999	66.50583593071066
2000	67.73625367922216
2001	68.69859635258528
2002	68.87311398298218
2003	70.51199133077417
2004	71.49784286975328
2005	71.81566737988703
2006	72.04499535491783
2007	72.33956053674773
2008	72.11723439330945