Year	per 1,000
1990	10.8
1991	10.7
1992	10.1
1993	9.8
1994	9.5
1995	9.3
1996	9
1997	8.8
1998	8.5
1999	8.2
2000	7.9
2001	7.7
2002	7.6
2003	7.4
2004	7.4
2005	7.4
2006	7.1
2007	6.9
2008	6.8
2009	6.6
2010	6.3
2011	6.1
2012	5.9
2013	5.7
2014	5.5
2015	5.4
2016	5.2
2017	5
2018	4.7
2019	4.5
2020	4.2
2021	4
2022	3.8