Year	per 1,000
1990	4
1991	4.2
1992	4.5
1993	4.7
1994	4.9
1995	5.1
1996	5.2
1997	5.2
1998	5.2
1999	5
2000	4.8
2001	4.6
2002	4.5
2003	4.4
2004	4.4
2005	4.4
2006	4.5
2007	4.6
2008	4.8
2009	5
2010	5.1
2011	5.3
2012	5.3
2013	5.3
2014	5.2
2015	5
2016	4.8
2017	4.4
2018	4.1
2019	5.9
2020	3.4
2021	3.1
2022	2.9