Year	per 1,000
1990	2.3
1991	2.2
1992	2.2
1993	2.2
1994	2.1
1995	2.1
1996	2.1
1997	2.3
1998	2.6
1999	2.8
2000	2.9
2001	2.8
2002	2.4
2003	2
2004	1.6
2005	1.4
2006	1.3
2007	1.3
2008	1.3
2009	1.3
2010	1.3
2011	1.3
2012	1.2
2013	1.2
2014	1.2
2015	1.1
2016	1.1
2017	1.1
2018	1
2019	1
2020	0.9
2021	0.9
2022	0.9