Year	per 1,000
1990	1.4
1991	1.4
1992	1.3
1993	1.2
1994	1.2
1995	1.1
1996	1.1
1997	1
1998	1
1999	1
2000	0.9
2001	0.9
2002	0.9
2003	0.8
2004	0.8
2005	0.8
2006	0.8
2007	0.7
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	0.4
2018	0.4
2019	0.4
2020	0.4
2021	0.4
2022	0.4