Year	per 1,000
1990	7.7
1991	6.6
1992	6.3
1993	6.1
1994	6
1995	5.8
1996	5.7
1997	5.6
1998	5.5
1999	5.4
2000	5.3
2001	5.3
2002	5.3
2003	5.6
2004	5.2
2005	5.2
2006	5.2
2007	5.1
2008	5.1
2009	5
2010	4.9
2011	5
2012	6.1
2013	6
2014	5.6
2015	5.9
2016	5.5
2017	5.6
2018	6
2019	5.4
2020	5
2021	4.9
2022	4.7