Year	per 1,000 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	3.118
1991	3.171
1992	3.223
1993	3.251
1994	3.286
1995	3.307
1996	3.326
1997	3.343
1998	3.355
1999	3.355
2000	3.375
2001	3.408
2002	3.435
2003	3.454
2004	3.473
2005	3.476
2006	3.469
2007	3.449
2008	3.443
2009	3.394
2010	3.397
2011	3.172
2012	3.188
2013	3.209
2014	3.225
2015	3.24
2016	3.255
2017	3.275
2018	3.276
2019	3.311
2020	3.324