Year	per 1,000
1990	2.3
1991	2.3
1992	2.4
1993	2.4
1994	2.3
1995	2.3
1996	2.3
1997	2.2
1998	2.2
1999	2.1
2000	2
2001	2
2002	1.9
2003	1.8
2004	1.8
2005	1.7
2006	1.7
2007	1.6
2008	1.6
2009	1.5
2010	1.5
2011	1.5
2012	1.5
2013	1.5
2014	1.4
2015	1.4
2016	1.4
2017	1.4
2018	1.4
2019	1.4
2020	1.3
2021	1.3
2022	1.3