Year	Percent
1991	3.08
1992	3.148
1993	2.881
1994	2.936
1995	2.789
1996	2.844
1997	2.846
1998	2.79
1999	2.876
2000	2.707
2001	2.668
2002	2.705
2003	2.452
2004	2.421
2005	2.304
2006	2.523
2007	2.922
2008	3.725
2009	3.942
2010	4.146
2011	4.046
2012	4.091
2013	4.275
2014	4.352
2015	4.535
2016	4.616
2017	4.646
2018	4.582
2019	4.472
2020	4.419
2021	4.359
2022	4.312