Year	per 1,000
1990	28.5
1991	27.8
1992	27.2
1993	26.5
1994	25.8
1995	25.2
1996	24.5
1997	23.9
1998	23.3
1999	22.7
2000	22
2001	21.5
2002	20.9
2003	20.3
2004	19.7
2005	19.2
2006	18.7
2007	18.2
2008	17.8
2009	17.3
2010	16.9
2011	16.5
2012	16.1
2013	15.7
2014	15.4
2015	15
2016	14.6
2017	14.2
2018	13.9
2019	13.5
2020	13.2
2021	12.8
2022	12.4