Year	per 1,000
1990	36.1
1991	44.9
1992	41.7
1993	44.9
1994	725.7
1995	50.1
1996	50.1
1997	47.5
1998	42.3
1999	36.1
2000	30.1
2001	25
2002	21.1
2003	18.1
2004	15.8
2005	14.1
2006	12.6
2007	11.5
2008	10.7
2009	10.1
2010	9.7
2011	9.4
2012	9.2
2013	9
2014	8.8
2015	8.4
2016	7.9
2017	7.3
2018	6.8
2019	6.3
2020	5.9
2021	5.7
2022	5.6