Year	% of total
1990	39.26106647394683
1991	38.99960108868201
1992	37.6482528020645
1993	36.94273437357285
1994	35.790859933963716
1995	35.62537275193248
1996	36.38803812022807
1997	37.01239853486447
1998	37.14674434085062
1999	37.59527864876983
2000	38.47239617565999
2001	39.35077520805661
2002	39.79559988315692
2003	41.26156635410122
2004	41.71944124236233
2005	42.26755413239138
2006	43.112911070712336
2007	44.155164222513065
2008	44.82837468404699