Year	per 1,000
1990	2.6
1991	2.5
1992	2.3
1993	2.2
1994	2.1
1995	2
1996	1.9
1997	2.2
1998	1.8
1999	1.8
2000	1.8
2001	1.7
2002	1.7
2003	1.7
2004	1.6
2005	1.6
2006	1.5
2007	1.5
2008	1.5
2009	1.4
2010	1.4
2011	1.4
2012	1.3
2013	1.3
2014	1.2
2015	1.2
2016	1.2
2017	1.1
2018	1.1
2019	1.1
2020	1
2021	1
2022	1