Year	per 1,000
1990	2.9
1991	2.1
1992	2
1993	1.9
1994	1.8
1995	1.7
1996	1.6
1997	1.5
1998	1.4
1999	1.4
2000	1.4
2001	1.4
2002	1.4
2003	1.4
2004	1.3
2005	1.3
2006	1.3
2007	1.3
2008	1.2
2009	1.2
2010	1.1
2011	1.1
2012	1
2013	1
2014	1
2015	0.9
2016	0.9
2017	0.9
2018	0.9
2019	0.9
2020	0.9
2021	0.9
2022	0.9