Year	per 1,000 people
1960	0.143
1965	0.161
1970	0.232
1975	0.234
1980	0.255
1981	0.255
1985	0.315
1986	0.335
1987	0.348
1988	0.367
1989	0.374
1990	0.392
1991	0.393
1992	0.411
1993	0.431
1994	0.449
1995	0.478
1996	0.496
1997	0.658
1999	0.683
2000	0.681
2002	0.723
2003	0.735
2004	0.72
2005	0.776
2006	0.828
2007	0.876
2008	0.907
2009	1.082
2010	1.148
2011	1.254
2012	1.305
2013	1.557
2014	1.489
2015	1.496
2016	1.589
2017	1.809
2018	1.888
2019	2.06
2020	2.228