Year	per 1,000
1990	1.9
1991	1.9
1992	1.8
1993	1.8
1994	1.7
1995	1.6
1996	1.5
1997	1.5
1998	1.4
1999	1.3
2000	1.2
2001	1.1
2002	1
2003	0.9
2004	0.9
2005	0.8
2006	0.7
2007	0.7
2008	0.6
2009	0.6
2010	0.6
2011	0.5
2012	0.5
2013	0.5
2014	0.4
2015	0.4
2016	0.4
2017	0.4
2018	0.4
2019	0.4
2020	0.4
2021	0.4
2022	0.4