Year	per 1000 people
1991	2.8
1992	2.8
1993	2.9
1994	3
1995	3.1
1996	3.1
1997	3.1
1998	3.2
1999	3.2
2000	3.3
2001	3.3
2002	3.3
2003	3.369
2006	3.44
2007	3.483
2008	3.531
2010	3.775
2011	3.87
2012	3.944
2013	4.039
2014	4.125
2015	4.191