Year	% of total
1990	44.56037399574862
1991	44.31384646119356
1992	43.95449579880636
1993	43.02221193836806
1994	42.89635183065918
1995	44.12329544219883
1996	44.946424494581336
1997	46.746333816415465
1998	48.787948707452536
1999	50.61049385006807
2000	51.21764802577626
2001	50.4679873424821
2002	50.50717802610262
2003	50.708458213308504
2004	50.68590146887302
2005	50.99261192710507
2006	51.29482730607306
2007	52.714252273434596
2008	52.69492471886434