Year	% of total
1990	69.82991579067894
1991	69.42380433696293
1992	68.75815674347885
1993	68.75206913036436
1994	67.62208611563162
1995	66.90017004046892
1996	65.96614551609345
1997	66.4089476017384
1998	68.88807118913581
1999	71.63934881300172
2000	71.01332203453036
2001	70.94106426299177
2002	72.20049472294522
2003	71.76405131932444
2004	71.35027816033022
2005	71.24507584231087
2006	72.3903686134306
2007	72.39306064272617
2008	74.49800874257595