Year	per 1,000
1990	2.8
1991	2.8
1992	2.8
1993	2.8
1994	2.7
1995	2.6
1996	2.6
1997	2.5
1998	2.4
1999	2.4
2000	2.3
2001	2.2
2002	2
2003	1.9
2004	1.8
2005	1.7
2006	1.6
2007	1.5
2008	1.4
2009	1.4
2010	1.3
2011	1.3
2012	1.3
2013	1.2
2014	1.2
2015	1.2
2016	1.2
2017	1.1
2018	1.1
2019	1.1
2020	1.1
2021	1.1
2022	1.2