Year	% of total
1990	22.775191713205523
1991	23.355894631678254
1992	23.022134895442267
1993	23.35707117991241
1994	24.11557211357066
1995	23.08567266155452
1996	21.915731484984786
1997	20.6167876762804
1998	19.55892299389309
1999	18.276444362764817
2000	17.441044158227186
2001	16.683409649619982
2002	16.928210072612277
2003	15.839665845283816
2004	14.952904762573118
2005	14.653004571193918
2006	14.431560572077897
2007	14.064897795301453
2008	14.222084383143528