Year	per 1,000 people
1960	0.946
1965	0.876
1970	0.822
1981	1.388
1984	1.886
1988	3
1990	3.641
1991	3.979
1992	4.345
1993	4.709
1994	4.966
1995	5.202
1996	5.485
1997	5.694
1998	5.754
1999	5.859
2000	5.943
2001	5.954
2002	6.005
2003	6.073
2004	6.21
2005	6.277
2006	6.349
2007	6.426
2008	6.611
2009	6.636
2010	6.776
2011	6.959
2012	7.256
2013	7.393
2014	7.551
2015	7.759
2016	7.949
2017	8.297
2018	8.427