Year	Percent
1998	20.29327
1999	17.74348
2000	17.42082
2001	16.17283
2002	13.11535
2003	10.42494
2004	10.95804
2005	11.77715
2006	13.15677
2007	14.32759
2008	15.09289
2009	17.7919
2010	16.27784
2011	16.08129
2012	16.43769
2013	16.89519
2014	16.37647
2015	17.65952