Year	per 1,000
1990	28.7
1991	28.3
1992	27.9
1993	27.6
1994	27.3
1995	26.9
1996	26.5
1997	26.1
1998	25.5
1999	24.9
2000	24.3
2001	23.6
2002	22.8
2003	22
2004	21.2
2005	20.4
2006	19.6
2007	18.7
2008	18
2009	17.3
2010	16.6
2011	16
2012	15.4
2013	14.9
2014	14.4
2015	13.9
2016	13.5
2017	13
2018	12.5
2019	12.1
2020	11.7
2021	11.3
2022	10.9