Year	Percent
1991	2.517
1992	3.53
1993	4.568
1994	4.421
1995	3.919
1996	4.084
1997	3.9886
1998	4.1352
1999	3.5688
2000	3.1305
2001	3.458
2002	3.0964
2003	4.487
2004	4.7641
2005	5.0916
2006	4.7095
2007	4.5137
2008	3.9666
2009	4.5202
2010	5.1886
2011	4.8001
2012	4.729
2013	4.9178
2014	4.9857
2015	4.9125
2016	5.0063
2017	5.0581