Year	per 1,000
1990	19.2
1991	17.9
1992	16.7
1993	15.6
1994	14.5
1995	13.5
1996	12.5
1997	11.6
1998	10.7
1999	9.9
2000	9.2
2001	8.6
2002	8
2003	7.6
2004	7.2
2005	7
2006	6.9
2007	7.1
2008	7.4
2009	7.9
2010	8.6
2011	9.5
2012	10.4
2013	11.5
2014	12.5
2015	13.2
2016	13.6
2017	13.7
2018	13.6
2019	13.3
2020	13.1
2021	12.8
2022	12.5