Year	Percent
1991	6.968
1992	8.303
1993	6.389
1994	5.664
1995	5.988
1996	4.931
1997	4.895
1998	4.611
1999	4.508
2000	4.433
2001	4.278
2002	4.257
2003	4.571
2004	4.938
2005	4.772
2006	4.499
2007	4.283
2008	4.222
2009	3.931
2010	3.447
2011	2.958
2012	2.534
2013	2.358
2014	2.213
2015	2.188
2016	2.266
2017	2.365
2018	2.363
2019	2.332
2020	2.289
2021	2.247
2022	2.24