Year	% of total
1990	23.833710578941265
1991	24.356240255574622
1992	23.97546933573505
1993	24.142467781175142
1994	24.873752138537327
1995	23.841628428663782
1996	22.717995918947718
1997	21.594417535800986
1998	20.60832946535709
1999	19.346324605527982
2000	18.4199742390639
2001	17.529595688414812
2002	17.7576726948706
2003	16.71483835095055
2004	15.877126238645829
2005	15.60332520002949
2006	15.444091501860553
2007	15.135545732087456
2008	15.246163520952162