Year	Percent
1977	2.23
1979	1.52
2002	0.76
2003	2.91
2004	3.58
2005	2.27
2006	2.21
2008	3.38
2009	1.95
2010	1.25
2011	2.97
2012	3.44
2013	4.29
2014	5.09
2015	4.83
2016	3.86
2017	3.91
2018	3.82
2019	3.54
2020	2.39