Year	per 1,000
1990	1.8
1991	1.8
1992	1.8
1993	1.8
1994	1.8
1995	1.7
1996	1.7
1997	1.7
1998	1.7
1999	1.8
2000	1.6
2001	1.6
2002	1.5
2003	1.5
2004	1.4
2005	1.3
2006	1.3
2007	1.2
2008	1.2
2009	1.1
2010	1.1
2011	1
2012	1
2013	1
2014	0.9
2015	0.9
2016	0.9
2017	0.9
2018	0.8
2019	0.8
2020	0.8
2021	0.8
2022	0.8