Year	per 1,000
1990	1.9
1991	1.9
1992	1.8
1993	1.8
1994	1.7
1995	1.7
1996	1.6
1997	1.5
1998	1.4
1999	1.3
2000	1.3
2001	1.2
2002	1.1
2003	1
2004	0.9
2005	0.9
2006	0.8
2007	0.8
2008	0.7
2009	0.7
2010	0.6
2011	0.6
2012	0.6
2013	0.5
2014	0.5
2015	0.5
2016	0.5
2017	0.5
2018	0.5
2019	0.5
2020	0.5
2021	0.5
2022	0.5