Year	per 1,000 people
1970	1.8
1971	1.9
1972	1.9
1973	1.9
1974	2
1975	2
1976	2.1
1977	2.1
1978	2.1
1979	2.2
1990	2.722
1991	2.676
1992	2.681
1993	2.868
1994	2.936
1995	3.001
1996	2.99
1997	3.12
1998	3.039
1999	3.088
2000	3.381
2001	3.443
2002	3.492
2003	3.509
2004	3.499
2005	3.539
2006	3.551
2007	3.561
2008	3.557
2009	3.584
2010	3.599
2011	3.637
2012	3.675
2013	3.688
2014	3.9345
2015	3.9516
2016	4.0194
2017	4.0676
2018	4.074
2019	4.119
2020	4.16
2021	5.469