Year	per 1,000
1990	3.5
1991	3.4
1992	3.2
1993	3
1994	2.9
1995	2.7
1996	2.6
1997	2.5
1998	2.4
1999	2.3
2000	2.2
2001	2.2
2002	2.1
2003	2
2004	3.3
2005	1.9
2006	1.9
2007	1.8
2008	1.8
2009	1.7
2010	1.6
2011	1.6
2012	1.5
2013	1.4
2014	1.3
2015	1.2
2016	1.2
2017	1.1
2018	1
2019	0.9
2020	0.9
2021	0.8
2022	0.8