Year	per 1,000
1990	7.5
1991	3.9
1992	3.6
1993	3.4
1994	3.3
1995	3.1
1996	3
1997	2.8
1998	2.8
1999	2.7
2000	2.6
2001	2.6
2002	2.6
2003	4.5
2004	2.6
2005	2.7
2006	2.7
2007	2.8
2008	2.8
2009	2.8
2010	2.8
2011	2.6
2012	2.5
2013	2.4
2014	2.2
2015	2.1
2016	1.9
2017	1.8
2018	1.7
2019	1.6
2020	1.6
2021	1.5
2022	1.4