Year	% of total
1990	35.13873825127908
1991	34.94990275188361
1992	34.02711506499793
1993	33.71097416225807
1994	33.00914868436764
1995	32.80376520734165
1996	33.20160635251252
1997	33.44339317132199
1998	33.368348493448984
1999	33.37647620065907
2000	33.908638452296685
2001	34.661550069158174
2002	35.11287744189834
2003	36.27961832979219
2004	36.76990069802479
2005	37.22689350971356
2006	37.85242635602984
2007	38.56476255194538
2008	39.12384591704956