Year	per 1,000
1990	1.8
1991	1.7
1992	1.5
1993	1.4
1994	1.3
1995	1.2
1996	1.2
1997	1.1
1998	1.1
1999	1
2000	1
2001	1
2002	1
2003	1
2004	1
2005	1
2006	1
2007	1
2008	1
2009	1
2010	1
2011	1
2012	1
2013	1
2014	1
2015	1
2016	1
2017	1
2018	1
2019	1
2020	1
2021	1
2022	1