Year	per 1,000
1990	9.5
1991	9.4
1992	9.2
1993	9.1
1994	9
1995	9
1996	8.9
1997	8.8
1998	8.6
1999	8.5
2000	8.4
2001	8.2
2002	8.1
2003	7.9
2004	7.7
2005	7.6
2006	7.4
2007	7.2
2008	7.1
2009	6.9
2010	6.7
2011	6.6
2012	6.4
2013	6.3
2014	6.1
2015	6
2016	5.8
2017	5.7
2018	5.5
2019	5.4
2020	5.2
2021	5.1
2022	5