Year	per 1,000
1990	1.6
1991	1.6
1992	1.5
1993	1.5
1994	1.5
1995	1.4
1996	1.4
1997	1.4
1998	1.3
1999	1.3
2000	1.3
2001	1.2
2002	1.2
2003	1.2
2004	1.2
2005	1.1
2006	1.1
2007	1.1
2008	1
2009	1
2010	1
2011	1
2012	0.9
2013	0.9
2014	0.9
2015	0.9
2016	0.8
2017	0.8
2018	0.8
2019	0.8
2020	0.8
2021	0.7
2022	0.7