Year	% of total
1990	18.675078542113113
1991	18.507225064767926
1992	18.052736927774937
1993	18.284891113787264
1994	17.577866904101196
1995	17.51093775630289
1996	17.14126973084061
1997	16.595224743298484
1998	16.165865566019487
1999	16.259067219957934
2000	15.443065784092674
2001	14.910664844966165
2002	14.264900758947306
2003	14.376799358870748
2004	13.355867962577264
2005	13.094446645787682
2006	12.488503127195184
2007	12.40336596690758
2008	12.718779222817025