Year	per 1,000
1990	10.4
1991	10
1992	9.7
1993	9.2
1994	8.8
1995	8.4
1996	8
1997	7.7
1998	7.3
1999	6.9
2000	6.6
2001	6.3
2002	6.1
2003	6
2004	6
2005	7.7
2006	6.5
2007	6.8
2008	7
2009	7.1
2010	7.1
2011	6.9
2012	6.8
2013	6.6
2014	6.5
2015	6.3
2016	6.2
2017	6
2018	5.9
2019	5.7
2020	5.6
2021	5.4
2022	5.3