Year	per 1,000
1990	4.8
1991	4.7
1992	4.6
1993	4.4
1994	4.2
1995	4
1996	3.9
1997	3.7
1998	3.5
1999	3.3
2000	3.1
2001	2.9
2002	2.7
2003	2.5
2004	2.3
2005	2.2
2006	2
2007	1.9
2008	1.7
2009	1.6
2010	1.5
2011	1.4
2012	1.3
2013	1.2
2014	1.1
2015	1.1
2016	1.1
2017	1.1
2018	1.1
2019	1.1
2020	1.1
2021	1.2
2022	1.3