Year	per 1,000
1990	33.6
1991	14.9
1992	14.8
1993	14.7
1994	14.5
1995	14.4
1996	14.4
1997	14.4
1998	14.3
1999	14.4
2000	14.3
2001	14.3
2002	14.3
2003	17.2
2004	14.1
2005	14
2006	13.8
2007	13.7
2008	13.5
2009	13.4
2010	13.3
2011	13.2
2012	13.1
2013	13.1
2014	13.1
2015	14.6
2016	13
2017	13.1
2018	13.1
2019	13
2020	12.8
2021	12.6
2022	12.2