Year	per 1,000
1990	18.8
1991	17.8
1992	16.7
1993	15.7
1994	14.7
1995	13.7
1996	12.7
1997	11.8
1998	10.9
1999	10
2000	9.2
2001	8.5
2002	7.8
2003	7.2
2004	6.7
2005	6.2
2006	5.8
2007	5.4
2008	5
2009	4.7
2010	4.5
2011	4.2
2012	4
2013	3.8
2014	3.6
2015	4.9
2016	3.3
2017	3.1
2018	3
2019	2.8
2020	2.7
2021	2.5
2022	2.4