Year % of total 1990 87.9678420957003 1991 87.52608513531374 1992 87.1810681247263 1993 86.88890959813075 1994 86.88861728032639 1995 87.10745164309526 1996 87.35857772410543 1997 87.62729892700644 1998 88.58837240923722 1999 89.03763976959098 2000 89.68469655065836 2001 89.4829487159142 2002 89.89122531572843 2003 89.862002571541 2004 89.73220852102114 2005 89.8830079823905 2006 89.197180619331 2007 89.47303855877257 2008 89.3886562615052