Year	%
1990	3.75092630712227
1997	3.53378684807256
1998	3.96341463414634
1999	3.6199460916442
2000	3.89556135770235
2001	4.25410928476233
2002	5.08583055863855
2003	5.81795058139535
2004	5.83741120757695
2005	6.35540780141844
2006	8.38098360655738
2007	8.49374255065554
2008	8.47923627684964
2009	8.41144219308701
2010	9.01106593087424
2011	8.93842010771993