Year	per 1,000
1990	5.3
1991	5.2
1992	5.2
1993	5.1
1994	5
1995	4.9
1996	4.9
1997	4.8
1998	4.7
1999	4.6
2000	4.5
2001	4.5
2002	4.4
2003	4.4
2004	4.4
2005	4.4
2006	4.4
2007	4.4
2008	4.4
2009	4.4
2010	4.4
2011	4.4
2012	4.3
2013	4.3
2014	4.3
2015	4.3
2016	4.3
2017	4.3
2018	4.3
2019	4.3
2020	4.3
2021	4.3
2022	4.7