Year	per 1,000
1990	1.9
1991	1.9
1992	1.9
1993	1.9
1994	1.9
1995	1.8
1996	1.8
1997	1.8
1998	1.7
1999	1.7
2000	1.6
2001	1.6
2002	1.5
2003	1.5
2004	1.5
2005	1.4
2006	1.4
2007	1.4
2008	1.3
2009	1.3
2010	1.2
2011	1.2
2012	1.1
2013	1.1
2014	1.1
2015	1
2016	1
2017	1
2018	0.9
2019	0.9
2020	0.9
2021	0.9
2022	0.9