Year	per 1,000
1990	5
1991	5
1992	5.1
1993	5.1
1994	5.2
1995	5.3
1996	5.3
1997	5.3
1998	5.3
1999	5.3
2000	5.3
2001	5.2
2002	5
2003	4.8
2004	4.7
2005	4.6
2006	4.6
2007	4.7
2008	4.8
2009	4.9
2010	5
2011	5.1
2012	5.2
2013	5.1
2014	5.1
2015	5
2016	4.9
2017	4.8
2018	4.7
2019	4.6
2020	4.5
2021	4.4
2022	4.3