Year	per 1,000
1990	1.6
1991	1.7
1992	1.4
1993	1.3
1994	1.2
1995	1.2
1996	1.2
1997	1.1
1998	1.1
1999	1.1
2000	1.1
2001	1.1
2002	1.1
2003	1.2
2004	1.2
2005	1.2
2006	1.3
2007	1.3
2008	1.3
2009	1.4
2010	1.4
2011	1.4
2012	1.4
2013	1.4
2014	1.4
2015	1.3
2016	1.3
2017	1.2
2018	1.2
2019	1.1
2020	1.1
2021	1
2022	0.9