Year	% of total
1990	2.310592176185947
1991	2.3672409194695874
1992	2.4045857996612403
1993	2.4603662028822453
1994	2.458377505204774
1995	2.9703770623530756
1996	3.5027125530353334
1997	3.993484375533659
1998	4.465510406572629
1999	4.89940456217326
2000	5.501847501207227
2001	5.5126953716555525
2002	5.7070186613742
2003	5.643644620145949
2004	5.586139184187574
2005	5.435615778619822
2006	5.420781067567546
2007	5.4572445844230035
2008	5.477244647116598