Year	% of total
1990	31.18889927348254
1991	31.43820907263339
1992	31.31657032750481
1993	31.24993489333987
1994	31.944218183579732
1995	31.336573591834803
1996	30.849047451363624
1997	30.523727010806994
1998	30.073820870436617
1999	29.34912467541868
2000	28.916341030145293
2001	28.3515604525438
2002	28.482127377853498
2003	27.488931776921422
2004	27.103022118147432
2005	26.899096236163295
2006	26.880155028833826
2007	26.775639967177405
2008	26.913107737625936