Year	per 1,000
1990	14.9
1991	14.7
1992	14.6
1993	14.5
1994	14.5
1995	14.6
1996	14.5
1997	14.5
1998	14.3
1999	14.1
2000	13.8
2001	13.5
2002	13.2
2003	12.8
2004	12.3
2005	11.8
2006	11.2
2007	10.5
2008	9.9
2009	9.2
2010	8.5
2011	7.9
2012	7.3
2013	6.7
2014	6.1
2015	5.6
2016	5.3
2017	5.1
2018	4.9
2019	4.8
2020	4.6
2021	4.5
2022	4.4