Year	per 1,000
1990	5.1
1991	4.9
1992	4.5
1993	4.1
1994	3.7
1995	3.4
1996	3.3
1997	3.2
1998	3.1
1999	3.1
2000	3
2001	2.9
2002	2.8
2003	2.7
2004	2.6
2005	2.4
2006	2.3
2007	2.1
2008	1.9
2009	1.8
2010	1.6
2011	1.5
2012	1.4
2013	1.3
2014	1.3
2015	1.3
2016	1.3
2017	1.3
2018	1.3
2019	1.3
2020	1.3
2021	1.4
2022	1.5