Year	Percent
1999	15.75671
2000	14.63877
2001	17.2922
2002	18.1109
2003	21.25587
2004	19.72832
2005	20.40062
2006	21.76618
2007	23.36529
2008	25.87045
2009	28.88676
2010	30.88002
2011	32.16701
2013	31.41247
2014	32.32513