Year	per 1000 people
1970	1.2
1971	1.3
1972	1.3
1973	1.4
1974	1.4
1975	1.5
1976	1.5
1977	1.6
1978	1.7
1979	1.8
1980	1.9
1981	2
1982	2.1
1983	2.1
1984	2.5
1985	2.7
1986	2.8
1987	2.8
1988	2.9
1989	3
1990	3.1
1991	3.067
1996	3.225
2007	3.674
2011	3.16
2012	3.175
2013	3.187
2014	3.215
2015	3.227
2016	3.238