Year	per 1,000
1990	5.8
1991	5.8
1992	5.9
1993	5.9
1994	6
1995	8
1996	5.9
1997	5.8
1998	5.6
1999	5.4
2000	5.2
2001	5.1
2002	4.9
2003	4.8
2004	4.7
2005	4.7
2006	4.6
2007	4.6
2008	4.5
2009	4.5
2010	4.4
2011	4.3
2012	4.3
2013	4.3
2014	4.3
2015	4.2
2016	4.2
2017	4.2
2018	4.1
2019	4.1
2020	4.1
2021	4
2022	4