Year	% of total
1990	28.264587189742624
1991	25.324155514555052
1992	25.910406209882005
1993	25.575841158631956
1994	25.311482513969604
1995	24.188396974971408
1996	23.211470680891082
1997	23.21360113015735
1998	23.048526063160786
1999	22.825768239814384
2000	21.926366373117457
2001	21.249151489337404
2002	20.68444563365002
2003	19.53405185653394
2004	19.61564327414157
2005	19.51942249363075
2006	19.410068608068
2007	19.34330828149337
2008	18.451945689765985