Year	per 1,000
1990	3
1991	2.7
1992	2.7
1993	2.9
1994	3.3
1995	3.9
1996	4.3
1997	4.3
1998	3.8
1999	3
2000	2.3
2001	1.9
2002	1.7
2003	1.7
2004	1.6
2005	1.6
2006	1.5
2007	1.5
2008	1.5
2009	1.4
2010	1.2
2011	1.1
2012	1
2013	0.9
2014	0.9
2015	0.9
2016	0.9
2017	0.9
2018	0.8
2019	0.8
2020	0.8
2021	0.7
2022	0.7