Year	per 1,000
1990	2.8
1991	3.2
1992	3.5
1993	3.9
1994	4.4
1995	4.8
1996	5.2
1997	5.6
1998	5.8
1999	6
2000	6.1
2001	6.1
2002	6.1
2003	6.1
2004	6
2005	6
2006	5.9
2007	5.9
2008	5.9
2009	5.8
2010	5.8
2011	5.8
2012	5.7
2013	5.6
2014	5.6
2015	5.5
2016	5.4
2017	5.3
2018	5.2
2019	5
2020	4.8
2021	4.6
2022	4.4