Year	per 1,000
1990	7.3
1991	7.3
1992	7.4
1993	7.5
1994	7.6
1995	7.7
1996	7.6
1997	7.5
1998	7.3
1999	7
2000	6.8
2001	6.5
2002	6.3
2003	6.1
2004	5.9
2005	5.8
2006	5.7
2007	5.6
2008	5.5
2009	5.3
2010	5.1
2011	4.9
2012	4.7
2013	4.6
2014	4.4
2015	4.2
2016	4.1
2017	4
2018	3.8
2019	3.8
2020	3.7
2021	3.6
2022	3.5