Year	% of total
1990	33.07345699014783
1991	32.962565585397144
1992	32.17180824962246
1993	31.994831859785236
1994	31.368454043753275
1995	31.258139661128446
1996	31.704284026287542
1997	31.95690602022112
1998	31.907660745848865
1999	31.965643555146272
2000	32.55115450817346
2001	33.30153089412925
2002	33.6184640899351
2003	34.56718742057759
2004	34.98026716577143
2005	35.28250992578707
2006	35.84342793840692
2007	36.350270891664344
2008	36.790920768193246