Year	per 1,000
1990	19.9
1991	22.4
1992	25.8
1993	29.8
1994	195.8
1995	33.6
1996	31.8
1997	28.7
1998	25.4
1999	22.3
2000	19.9
2001	17.9
2002	16.3
2003	15
2004	13.6
2005	12.3
2006	10.9
2007	9.7
2008	8.6
2009	7.6
2010	6.8
2011	6.2
2012	5.8
2013	5.6
2014	5.5
2015	5.5
2016	5.7
2017	5.9
2018	6.2
2019	6.4
2020	6.6
2021	6.7
2022	6.7