Year	% of total
1990	25.865552587716884
1991	25.866276680377325
1992	26.181851494605116
1993	26.67098218024451
1994	26.938110318635477
1995	27.46442210044724
1996	27.615945955561852
1997	27.990675944907146
1998	28.48912851201925
1999	28.842098189269386
2000	28.851694606720326
2001	29.10722851263871
2002	29.66343659532227
2003	29.54296267337496
2004	29.892928436761505
2005	30.29974598854305
2006	30.286283481978877
2007	30.598648708236627
2008	30.27612286123498