Year	per 1,000
1990	5.3
1991	4.7
1992	4.2
1993	3.8
1994	3.5
1995	3.2
1996	3
1997	2.8
1998	2.6
1999	2.5
2000	2.3
2001	2.2
2002	2.1
2003	2
2004	3.1
2005	1.9
2006	1.9
2007	2
2008	2
2009	2.1
2010	2.2
2011	2.2
2012	2.3
2013	2.3
2014	2.3
2015	2.3
2016	2.3
2017	2.3
2018	2.2
2019	2.2
2020	2.1
2021	2.1
2022	2