Year	per 1,000
1990	14.7
1991	14.3
1992	14
1993	13.7
1994	13.4
1995	13.2
1996	12.9
1997	12.7
1998	12.4
1999	12.2
2000	12
2001	11.8
2002	11.7
2003	11.5
2004	11.4
2005	11.3
2006	11.3
2007	11.2
2008	11.2
2009	11.2
2010	11.2
2011	11.3
2012	11.3
2013	11.4
2014	11.4
2015	11.4
2016	11.4
2017	11.3
2018	11.2
2019	11.2
2020	11.1
2021	11
2022	10.9