Year	per 1,000
1990	8.8
1991	8.4
1992	7.9
1993	7.6
1994	7.2
1995	6.9
1996	6.5
1997	6.2
1998	6
1999	5.7
2000	5.4
2001	5.2
2002	5.1
2003	4.9
2004	4.7
2005	4.5
2006	4.4
2007	4.2
2008	4
2009	6.3
2010	3.8
2011	3.7
2012	3.6
2013	3.6
2014	3.6
2015	3.6
2016	3.6
2017	3.6
2018	3.5
2019	3.5
2020	3.4
2021	3.3
2022	3.2