| 年份 | 日本 |
|---|---|
| 2023 | - |
| 2022 | - |
| 2021 | 2.4 |
| 2020 | 2.5 |
| 2019 | 2.6 |
| 2018 | 2.7 |
| 2017 | 2.7 |
| 2016 | 2.8 |
| 2015 | 2.9 |
| 2014 | 3 |
| 2013 | 3.1 |
| 2012 | 3.2 |
| 2011 | 3.4 |
| 2010 | 3.4 |
| 2009 | 3.5 |
| 2008 | 3.6 |
| 2007 | 3.8 |
| 2006 | 3.9 |
| 2005 | 4 |
| 2004 | 4.1 |
| 2003 | 4.3 |
| 2002 | 4.4 |
| 2001 | 4.6 |
| 2000 | 4.9 |
| 1999 | 5.1 |
| 1998 | 5.4 |
| 1997 | 5.6 |
| 1996 | 5.9 |
| 1995 | 6.2 |
| 1994 | 6.4 |
| 1993 | 6.5 |
| 1992 | 6.7 |
| 1991 | 6.8 |
| 1990 | 6.9 |
| 1989 | 7 |
| 1988 | 7.2 |
| 1987 | 7.5 |
| 1986 | 7.8 |
| 1985 | 8.2 |
| 1984 | 8.7 |
| 1983 | 9.2 |
| 1982 | 9.8 |
| 1981 | 10.4 |
| 1980 | 11 |
| 1979 | 11.7 |
| 1978 | 12.4 |
| 1977 | 13.2 |
| 1976 | 14 |
| 1975 | 14.9 |
| 1974 | 15.8 |
| 1973 | 16.7 |
| 1972 | 17.6 |
| 1971 | 18.5 |
| 1970 | 19.6 |
| 1969 | 20.7 |
| 1968 | 22.1 |
| 1967 | 23.5 |
| 1966 | 25.3 |
| 1965 | 27.5 |
| 1964 | 30 |
| 1963 | 32.8 |
| 1962 | 36.1 |
| 1961 | 39.8 |
| 1960 | 43.3 |