Year	Percent
1990	2.35
1991	2.39
1992	2.6
1993	2.8
1994	3.14
1995	3.48
1996	3.39
1997	3.07
1998	2.85
1999	2.77
2000	2.63
2001	2.54
2002	2.44
2003	2.31
2004	2.14
2005	2.01
2006	1.91
2007	1.82
2008	1.74
2009	1.73
2010	1.68
2011	1.65
2012	1.65
2013	1.64
2014	1.64
2015	1.66
2016	1.67
2017	1.66
2018	1.65
2019	1.64