Year	per 1,000
1990	8.5
1991	8.2
1992	7.9
1993	7.7
1994	7.6
1995	7.6
1996	7.6
1997	7.7
1998	7.8
1999	7.9
2000	7.9
2001	7.8
2002	7.7
2003	7.6
2004	7.5
2005	7.5
2006	7.6
2007	7.6
2008	7.6
2009	7.4
2010	7.2
2011	6.9
2012	6.5
2013	6.1
2014	5.8
2015	5.6
2016	5.4
2017	5.3
2018	5.3
2019	5.5
2020	5.9
2021	6.6
2022	7.7