Year	per 1,000
1990	29.6
1991	30.9
1992	32.2
1993	58.8
1994	34
1995	34.1
1996	33.4
1997	31.9
1998	30
1999	27.7
2000	25.3
2001	22.8
2002	20.6
2003	18.7
2004	16.9
2005	15.1
2006	13.6
2007	12.2
2008	11.1
2009	10.4
2010	9.8
2011	9.5
2012	9.4
2013	9.3
2014	9.2
2015	9.2
2016	9.1
2017	8.9
2018	8.8
2019	8.6
2020	8.4
2021	8.2
2022	8