Year	% of total
1990	63.375192479328724
1991	63.27210869972576
1992	63.57056297021478
1993	63.073170778850624
1994	62.70224107646905
1995	61.5135574170247
1996	61.67236087395022
1997	62.82919863914769
1998	64.59862079359493
1999	65.50838249887995
2000	65.11243110448396
2001	66.21097648090745
2002	66.10779661357346
2003	67.0762548628787
2004	67.5662416106536
2005	67.12545388606178
2006	67.84094207561176
2007	68.44149228135385
2008	70.81942047174462