Year	per 1,000
1990	5.5
1991	5.5
1992	5.7
1993	5.8
1994	5.7
1995	5.8
1996	5.8
1997	5.8
1998	5.9
1999	6
2000	6
2001	6
2002	6
2003	5.8
2004	6
2005	5.6
2006	5.5
2007	5.3
2008	5.2
2009	5
2010	4.9
2011	4.7
2012	4.6
2013	4.6
2014	4.5
2015	4.5
2016	4.5
2017	4.5
2018	4.5
2019	4.5
2020	4.5
2021	4.4
2022	4.5