Year	Percent
1991	2.642
1992	3.605
1993	4.604
1994	4.181
1995	3.977
1996	4.2421
1997	4.2123
1998	3.9241
1999	3.2692
2000	3.0985
2001	3.355
2002	3.2189
2003	4.0416
2004	4.585
2005	4.6445
2006	4.476
2007	4.1565
2008	3.5942
2009	4.1179
2010	4.9312
2011	4.4783
2012	4.4668
2013	4.6506
2014	4.8249
2015	4.6427
2016	4.9369
2017	5.0965