Year	per 1,000
1990	9.8
1991	9.6
1992	9.4
1993	9.2
1994	9.1
1995	8.9
1996	8.8
1997	8.7
1998	8.5
1999	8.4
2000	8.3
2001	8.2
2002	8.1
2003	8
2004	7.9
2005	7.9
2006	7.9
2007	7.8
2008	7.8
2009	7.8
2010	7.7
2011	7.7
2012	7.7
2013	7.7
2014	7.7
2015	7.8
2016	7.8
2017	7.8
2018	7.8
2019	7.8
2020	7.7
2021	7.7
2022	7.6