Year per 1000 people 1961 1.1 1962 1.2 1963 1.3 1964 1.3 1965 1.3 1966 1.3 1967 1.3 1968 1.3 1969 1.4 1970 1.4 1971 1.5 1972 1.6 1973 1.6 1974 1.6 1975 1.7 1976 1.7 1977 1.7 1978 1.8 1979 1.8 1980 1.8 1981 1.8 1982 1.9 1983 1.9 1984 1.9 1985 2 1986 2 1987 2.1 1988 2.1 1989 2.1 1990 2.1 1991 2.1 1992 2.1 1993 2.2 1994 2.1 1995 2.1 1996 2.1 1997 2.1 1998 1.863 1999 2.1 2001 1.889 2002 1.899 2004 1.899 2006 1.911 2008 1.961 2010 2.041 2013 2.453 2014 2.497 2015 2.539