Year	% of total
1990	25.7705899949826
1991	25.81269796142033
1992	25.84653461728534
1993	26.043759339480253
1994	26.034929457670074
1995	26.211036073208064
1996	26.301201975051697
1997	27.559904086225707
1998	27.75256523067559
1999	27.7618277306275
2000	28.328842336401166
2001	29.604501198324975
2002	30.82782836075911
2003	32.20407961803535
2004	33.16754140982555
2005	34.232578681683236
2006	35.86746766413997
2007	37.60301122756292
2008	38.77855725444063