Year	per 1,000
1990	41.9
1991	46.1
1992	52
1993	58.7
1994	182.3
1995	63.6
1996	59.5
1997	53.2
1998	46.4
1999	40.3
2000	35.4
2001	31.5
2002	28.2
2003	25.4
2004	22.8
2005	20.2
2006	17.7
2007	15.4
2008	13.4
2009	11.7
2010	10.3
2011	9.2
2012	8.5
2013	8
2014	7.7
2015	7.7
2016	7.7
2017	7.9
2018	8.2
2019	8.3
2020	8.4
2021	8.4
2022	8.4