Year	Percent
1991	1.221
1992	2.263
1993	3.071
1994	3.467
1995	2.879
1996	3.4121
1997	4.3714
1998	3.1706
1999	2.8083
2000	2.2981
2001	1.7027
2002	2.7812
2003	3.8092
2004	3.9439
2005	3.8863
2006	3.4029
2007	2.9295
2008	2.8208
2009	3.769
2010	4.4843
2011	4.075
2012	4.2764
2013	4.6001
2014	4.6874
2015	4.7036
2016	4.8407
2017	4.5696