Year	% of total
1990	37.75064768352162
1991	36.25448030601651
1992	35.996951787613945
1993	37.605671564693296
1994	38.71192760528449
1995	39.264268922097116
1996	39.64047955537261
1997	38.94777434540955
1998	38.012760089409376
1999	37.534939873094274
2000	37.734319299110794
2001	39.50513702537917
2002	38.69691930599046
2003	38.75595325508578
2004	38.42893328305648
2005	38.931782817922304
2006	38.770135607036146
2007	37.67226415436697
2008	38.07234459611095