Year	per 1,000
1990	8.7
1991	8.6
1992	8.5
1993	8.5
1994	8.6
1995	8.7
1996	8.8
1997	8.8
1998	8.7
1999	8.7
2000	8.6
2001	8.6
2002	8.6
2003	8.5
2004	8.4
2005	8.2
2006	8.1
2007	8.1
2008	8.1
2009	8.1
2010	8
2011	8
2012	8
2013	8
2014	8.1
2015	8.1
2016	8.1
2017	8
2018	7.9
2019	7.7
2020	7.6
2021	7.6
2022	7.6