Year	per 1,000
1990	2.9
1991	2.9
1992	2.8
1993	2.7
1994	2.6
1995	2.6
1996	2.5
1997	2.4
1998	2.4
1999	2.3
2000	2.2
2001	2.1
2002	2.1
2003	2
2004	2.3
2005	1.9
2006	1.9
2007	1.8
2008	2.3
2009	1.7
2010	1.7
2011	1.7
2012	1.6
2013	1.6
2014	1.5
2015	1.5
2016	1.5
2017	1.4
2018	1.4
2019	1.4
2020	1.3
2021	1.3
2022	1.3