Year	per 1,000
1990	9.7
1991	12.7
1992	9.8
1993	10
1994	10
1995	9.8
1996	9.2
1997	8.2
1998	6.9
1999	5.7
2000	5
2001	4.8
2002	4.9
2003	5.1
2004	5.4
2005	5.6
2006	5.8
2007	5.8
2008	5.6
2009	5.3
2010	5
2011	4.8
2012	4.9
2013	5.1
2014	5.6
2015	6
2016	6.3
2017	6.3
2018	5.9
2019	5.2
2020	4.4
2021	3.7
2022	3.1