Year	per 1,000
1990	2.9
1991	2.9
1992	2.8
1993	2.7
1994	2.7
1995	4.6
1996	2.5
1997	2.4
1998	2.4
1999	2.3
2000	2.2
2001	2.1
2002	2
2003	2
2004	1.9
2005	1.8
2006	1.7
2007	1.7
2008	1.6
2009	1.5
2010	1.4
2011	1.3
2012	1.2
2013	1.2
2014	1.1
2015	1
2016	1
2017	0.9
2018	0.9
2019	0.9
2020	0.8
2021	0.8
2022	0.8