| Year | Value |
|---|---|
| 1914 | $1.00 |
| 1915 | $1.01 |
| 1916 | $1.03 |
| 1917 | $1.16 |
| 1918 | $1.37 |
| 1919 | $1.65 |
| 1920 | $1.89 |
| 1921 | $1.94 |
| 1922 | $1.73 |
| 1923 | $1.69 |
| 1924 | $1.73 |
| 1925 | $1.73 |
| 1926 | $1.79 |
| 1927 | $1.77 |
| 1928 | $1.73 |
| 1929 | $1.71 |
| 1930 | $1.72 |
| 1931 | $1.61 |
| 1932 | $1.46 |
| 1933 | $1.31 |
| 1934 | $1.32 |
| 1935 | $1.34 |
| 1936 | $1.38 |
| 1937 | $1.40 |
| 1938 | $1.44 |
| 1939 | $1.40 |
| 1940 | $1.40 |
| 1941 | $1.41 |
| 1942 | $1.55 |
| 1943 | $1.69 |
| 1944 | $1.74 |
| 1945 | $1.78 |
| 1946 | $1.82 |
| 1947 | $2.15 |
| 1948 | $2.34 |
| 1949 | $2.41 |
| 1950 | $2.36 |
| 1951 | $2.50 |
| 1952 | $2.65 |
| 1953 | $2.67 |
| 1954 | $2.69 |
| 1955 | $2.67 |
| 1956 | $2.68 |
| 1957 | $2.76 |
| 1958 | $2.84 |
| 1959 | $2.89 |
| 1960 | $2.94 |
| 1961 | $2.98 |
| 1962 | $3.00 |
| 1963 | $3.04 |
| 1964 | $3.09 |
| 1965 | $3.12 |
| 1966 | $3.18 |
| 1967 | $3.29 |
| 1968 | $3.39 |
| 1969 | $3.55 |
| 1970 | $3.77 |
| 1971 | $3.98 |
| 1972 | $4.11 |
| 1973 | $4.25 |
| 1974 | $4.62 |
| 1975 | $5.19 |
| 1976 | $5.55 |
| 1977 | $5.82 |
| 1978 | $6.21 |
| 1979 | $6.77 |
| 1980 | $7.67 |
| 1981 | $8.63 |
| 1982 | $9.40 |
| 1983 | $9.76 |
| 1984 | $10.13 |
| 1985 | $10.53 |
| 1986 | $10.93 |
| 1987 | $11.05 |
| 1988 | $11.54 |
| 1989 | $12.05 |
| 1990 | $12.61 |
| 1991 | $13.38 |
| 1992 | $13.79 |
| 1993 | $14.19 |
| 1994 | $14.58 |
| 1995 | $14.97 |
| 1996 | $15.35 |
| 1997 | $15.86 |
| 1998 | $16.13 |
| 1999 | $16.39 |
| 2000 | $16.83 |
| 2001 | $17.40 |
| 2002 | $17.67 |
| 2003 | $18.09 |
| 2004 | $18.43 |
| 2005 | $19.03 |
| 2006 | $19.68 |
| 2007 | $20.18 |
| 2008 | $21.00 |
| 2009 | $21.02 |
| 2010 | $21.59 |
| 2011 | $21.92 |
| 2012 | $22.57 |
| 2013 | $22.96 |
| 2014 | $23.30 |
| 2015 | $23.48 |
| 2016 | $23.65 |
| 2017 | $24.14 |
| 2018 | $24.65 |
| 2019 | $25.12 |
| 2020 | $25.70 |
| 2021 | $26.05 |
| 2022 | $27.88 |
| 2023 | $29.68 |
| 2024 | $30.67 |