Year	per 1,000
1990	8.1
1991	8.3
1992	8.3
1993	8.1
1994	7.9
1995	7.5
1996	7.3
1997	7.1
1998	7
1999	6.9
2000	6.9
2001	6.9
2002	6.9
2003	7.1
2004	7.2
2005	7.3
2006	7.4
2007	7.3
2008	7.1
2009	6.9
2010	6.7
2011	6.5
2012	6.4
2013	6.4
2014	6.4
2015	6.5
2016	6.4
2017	6.1
2018	5.7
2019	5.4
2020	5.1
2021	4.9
2022	4.8