Year	per 1,000
1990	16.5
1991	24.9
1992	14.9
1993	14.3
1994	13.8
1995	13.2
1996	12.5
1997	11.3
1998	9.6
1999	8
2000	6.9
2001	6.3
2002	6
2003	6.1
2004	6.4
2005	6.6
2006	6.7
2007	6.6
2008	6.3
2009	5.8
2010	5.2
2011	4.7
2012	4.3
2013	3.9
2014	3.6
2015	3.4
2016	3.3
2017	3.2
2018	3.1
2019	2.9
2020	2.8
2021	2.6
2022	2.5