Year per 1000 people 1960 1 1961 1 1962 1.1 1963 1.1 1964 1.2 1965 1.2 1966 1.3 1967 1.3 1968 1.4 1969 1.4 1970 1.4 1971 1.5 1972 1.5 1973 1.5 1974 1.6 1975 1.6 1976 1.6 1977 1.7 1978 1.7 1979 1.7 1980 1.8 1981 1.8 1982 1.8 1983 1.9 1984 1.9 1985 2 1986 2 1987 2.1 1988 2.1 1989 2.1 1990 2.1 1991 2.2 1992 2.2 1993 2.2 1994 2.3 1995 2.3 1996 2.4 1997 2.4 1998 2.3 1999 2.3 2000 2.2 2001 2.3 2002 2.3 2003 2.469 2005 1.97 2006 2.012 2008 2.144 2010 2.157 2011 2.182 2012 2.202 2013 2.207 2014 2.271 2015 2.29