Year	% of total
1990	12.379551875757974
1991	12.787466593386625
1992	13.262745479860772
1993	13.602972799984379
1994	13.741724266285193
1995	14.148004219897617
1996	14.30866392208528
1997	14.739214731133107
1998	15.30815355219944
1999	15.33256563290022
2000	15.262236006452673
2001	15.008372604540014
2002	15.131679640917548
2003	15.77357808398869
2004	15.040870985768219
2005	15.404616876263894
2006	14.910994209807257
2007	14.585343140568739
2008	15.176286884887237