Year	per 1,000
1990	2.3
1991	2.2
1992	2.2
1993	2.2
1994	2.1
1995	2.1
1996	2.1
1997	2
1998	2
1999	1.9
2000	1.9
2001	1.9
2002	1.9
2003	1.8
2004	1.8
2005	1.8
2006	1.8
2007	1.8
2008	1.8
2009	1.8
2010	1.8
2011	1.8
2012	1.8
2013	1.8
2014	1.8
2015	1.8
2016	1.8
2017	1.8
2018	1.8
2019	1.8
2020	1.8
2021	1.8
2022	1.9