Year	per 1,000
1990	9.7
1991	9.4
1992	9.2
1993	9
1994	8.7
1995	8.5
1996	8.3
1997	8.2
1998	8.2
1999	8.4
2000	8.5
2001	8.4
2002	7.8
2003	7
2004	6.3
2005	5.7
2006	5.4
2007	5.3
2008	5.3
2009	5.4
2010	5.4
2011	5.3
2012	5.2
2013	5
2014	4.8
2015	4.7
2016	4.6
2017	4.5
2018	4.4
2019	4.4
2020	4.4
2021	4.4
2022	4.5