Year	per 1,000
1990	13.8
1991	15.8
1992	12.8
1993	12
1994	11.1
1995	10.4
1996	9.8
1997	9.6
1998	9.6
1999	9.7
2000	9.4
2001	8.9
2002	8.1
2003	7.4
2004	6.8
2005	6.3
2006	5.9
2007	5.7
2008	5.7
2009	5.8
2010	5.9
2011	6
2012	5.9
2013	5.7
2014	5.2
2015	4.7
2016	4.2
2017	4
2018	4.2
2019	4.5
2020	5
2021	5.5
2022	5.9