Year	per 1,000
1990	2.6
1991	2.4
1992	2.3
1993	2.2
1994	2.1
1995	1.9
1996	1.8
1997	1.6
1998	1.5
1999	1.4
2000	1.3
2001	1.2
2002	1.1
2003	1
2004	0.9
2005	0.8
2006	0.8
2007	0.7
2008	0.7
2009	0.6
2010	0.6
2011	0.6
2012	0.5
2013	0.5
2014	0.5
2015	0.4
2016	0.4
2017	0.4
2018	0.4
2019	0.4
2020	0.4
2021	0.4
2022	0.3