Year	per 1,000
1990	14.3
1991	13.5
1992	12.8
1993	12
1994	11.4
1995	10.8
1996	10.2
1997	9.7
1998	9.3
1999	8.9
2000	8.6
2001	8.4
2002	8.2
2003	8.1
2004	8
2005	7.8
2006	7.8
2007	7.7
2008	7.6
2009	7.6
2010	7.5
2011	7.5
2012	7.4
2013	7.3
2014	7.3
2015	7.2
2016	7.2
2017	7.1
2018	7
2019	6.9
2020	6.9
2021	6.8
2022	6.7