Year	per 1,000
1990	7.3
1991	7.7
1992	8.2
1993	8.5
1994	8.7
1995	8.7
1996	8.6
1997	8.4
1998	8.2
1999	8
2000	7.9
2001	7.8
2002	7.6
2003	7.4
2004	7.2
2005	7.1
2006	7
2007	6.7
2008	6.5
2009	6.2
2010	5.8
2011	5.4
2012	5.1
2013	4.8
2014	4.5
2015	4.2
2016	3.9
2017	3.7
2018	3.6
2019	3.5
2020	3.4
2021	3.3
2022	3.2