Year	per 1000 people
1980	1.033
1981	1.089
1982	1.17
1983	1.207
1984	1.28
1985	1.362
1986	1.419
1987	1.485
1988	1.52
1989	1.557
1990	1.57
1991	1.555
1998	1.427
1999	1.401
2000	1.422
2001	1.338
2003	1.34
2005	1.418
2009	1.65
2010	1.738
2011	1.796
2012	1.835
2013	1.886