Year	per 1,000
1990	5.5
1991	5.5
1992	5.4
1993	5.3
1994	5.3
1995	5.2
1996	5.2
1997	5.1
1998	5.1
1999	5
2000	4.9
2001	4.8
2002	4.7
2003	4.6
2004	4.4
2005	4.3
2006	4.2
2007	4
2008	3.9
2009	3.8
2010	3.8
2011	3.7
2012	3.7
2013	3.7
2014	3.8
2015	3.8
2016	3.9
2017	3.9
2018	3.9
2019	3.9
2020	3.9
2021	3.9
2022	3.8