Year	per 1,000
1990	1.9
1991	2
1992	1.6
1993	1.5
1994	1.4
1995	1.3
1996	1.3
1997	1.3
1998	1.2
1999	1.2
2000	1.2
2001	1.2
2002	1.2
2003	1.2
2004	1.2
2005	1.2
2006	1.2
2007	1.2
2008	1.3
2009	1.3
2010	1.3
2011	1.3
2012	1.3
2013	1.2
2014	1.2
2015	1.2
2016	1.1
2017	1
2018	1
2019	0.9
2020	0.8
2021	0.8
2022	0.7