Year	per 1,000
1990	2.5
1991	2.5
1992	2.5
1993	2.6
1994	2.6
1995	2.6
1996	2.6
1997	2.6
1998	5.2
1999	2.7
2000	2.7
2001	2.7
2002	2.7
2003	2.7
2004	2.7
2005	2.8
2006	2.7
2007	2.7
2008	2.7
2009	2.7
2010	2.6
2011	2.5
2012	2.5
2013	2.4
2014	2.4
2015	2.3
2016	2.3
2017	2.2
2018	2.2
2019	2.1
2020	2.1
2021	2
2022	2