Year	per 1,000
1990	14.5
1991	14
1992	13.5
1993	13.2
1994	12.9
1995	12.6
1996	12.4
1997	12.1
1998	11.9
1999	11.7
2000	11.5
2001	11.3
2002	11
2003	10.8
2004	10.5
2005	10.3
2006	10
2007	9.7
2008	9.4
2009	9
2010	8.7
2011	8.3
2012	7.9
2013	7.5
2014	7.1
2015	6.8
2016	6.4
2017	6.1
2018	5.8
2019	5.5
2020	5.2
2021	5
2022	4.8