Year	per 1,000
1990	9.1
1991	9.1
1992	9.2
1993	9.4
1994	9.8
1995	10.3
1996	10.8
1997	11.2
1998	11.3
1999	11.2
2000	11
2001	10.8
2002	10.6
2003	10.4
2004	10.1
2005	9.9
2006	9.6
2007	9.4
2008	9.3
2009	9.4
2010	9.6
2011	9.9
2012	10.2
2013	10.3
2014	10.2
2015	9.8
2016	9.3
2017	8.8
2018	8.2
2019	7.7
2020	7.3
2021	7
2022	6.8