Year	Percent
1997	36.28855
1999	32.34944
2000	28.20551
2001	30.24759
2002	30.28029
2003	28.17706
2004	31.37897
2005	23.41832
2006	23.86542
2007	18.98153
2008	17.79834
2009	18.18657
2010	18.56976
2011	18.94274
2012	18.96233
2013	20.02528
2014	21.481