Year	per 1,000
1990	8.8
1991	8.7
1992	8.5
1993	8.4
1994	8.2
1995	8.1
1996	8
1997	7.9
1998	10
1999	7.6
2000	7.5
2001	7.4
2002	7.3
2003	7.2
2004	7
2005	6.9
2006	6.8
2007	6.7
2008	6.5
2009	6.4
2010	6.2
2011	6.1
2012	6
2013	5.8
2014	5.7
2015	5.5
2016	5.4
2017	5.2
2018	5.1
2019	5
2020	4.8
2021	4.7
2022	4.5