Year	per 1,000
1990	2.8
1991	2.8
1992	2.8
1993	2.8
1994	2.8
1995	2.7
1996	2.6
1997	2.5
1998	2.4
1999	2.4
2000	2.3
2001	2.3
2002	2.2
2003	2.2
2004	2.1
2005	1.9
2006	1.8
2007	1.7
2008	1.6
2009	1.5
2010	1.4
2011	1.4
2012	1.3
2013	1.2
2014	1.2
2015	1.1
2016	1.1
2017	1
2018	0.9
2019	0.8
2020	0.8
2021	0.7
2022	0.7