U.S. Energy Information Administration
May 2011 Monthly Energy Review
Note: Information about data precision and revisions.
Release Date: May 26, 2011
Next Update: Last week of June 2011
Table 9.4. Motor Gasoline Retail Prices, U.S. City Average
| Year | Leaded Regular Gasoline, U.S. City Average Retail Price (Dollars per Gallon Excluding Taxes) | Unleaded Regular Gasoline, U.S. City Average Retail Price (Dollars per Gallon Excluding Taxes) | Unleaded Premium Gasoline, U.S. City Average Retail Price (Dollars per Gallon Excluding Taxes) | All Types of Gasoline, U.S. City Average Retail Price (Dollars per Gallon Excluding Taxes) |
| 1973 January | Not Available | Not Available | Not Available | Not Available |
| 1973 February | Not Available | Not Available | Not Available | Not Available |
| 1973 March | Not Available | Not Available | Not Available | Not Available |
| 1973 April | Not Available | Not Available | Not Available | Not Available |
| 1973 May | Not Available | Not Available | Not Available | Not Available |
| 1973 June | Not Available | Not Available | Not Available | Not Available |
| 1973 July | Not Available | Not Available | Not Available | Not Available |
| 1973 August | Not Available | Not Available | Not Available | Not Available |
| 1973 September | Not Available | Not Available | Not Available | Not Available |
| 1973 October | 0.402 | Not Available | Not Available | Not Available |
| 1973 November | 0.418 | Not Available | Not Available | Not Available |
| 1973 December | 0.437 | Not Available | Not Available | Not Available |
| 1973 Average | 0.388 | Not Available | Not Available | Not Available |
| 1974 January | 0.465 | Not Available | Not Available | Not Available |
| 1974 February | 0.491 | Not Available | Not Available | Not Available |
| 1974 March | 0.528 | Not Available | Not Available | Not Available |
| 1974 April | 0.537 | Not Available | Not Available | Not Available |
| 1974 May | 0.55 | Not Available | Not Available | Not Available |
| 1974 June | 0.556 | Not Available | Not Available | Not Available |
| 1974 July | 0.558 | Not Available | Not Available | Not Available |
| 1974 August | 0.554 | Not Available | Not Available | Not Available |
| 1974 September | 0.55 | Not Available | Not Available | Not Available |
| 1974 October | 0.534 | Not Available | Not Available | Not Available |
| 1974 November | 0.528 | Not Available | Not Available | Not Available |
| 1974 December | 0.528 | Not Available | Not Available | Not Available |
| 1974 Average | 0.532 | Not Available | Not Available | Not Available |
| 1975 January | 0.532 | Not Available | Not Available | Not Available |
| 1975 February | 0.533 | Not Available | Not Available | Not Available |
| 1975 March | 0.534 | Not Available | Not Available | Not Available |
| 1975 April | 0.54 | Not Available | Not Available | Not Available |
| 1975 May | 0.55 | Not Available | Not Available | Not Available |
| 1975 June | 0.567 | Not Available | Not Available | Not Available |
| 1975 July | 0.591 | Not Available | Not Available | Not Available |
| 1975 August | 0.595 | Not Available | Not Available | Not Available |
| 1975 September | 0.597 | Not Available | Not Available | Not Available |
| 1975 October | 0.594 | Not Available | Not Available | Not Available |
| 1975 November | 0.589 | Not Available | Not Available | Not Available |
| 1975 December | 0.586 | Not Available | Not Available | Not Available |
| 1975 Average | 0.567 | Not Available | Not Available | Not Available |
| 1976 January | 0.584 | 0.605 | Not Available | Not Available |
| 1976 February | 0.578 | 0.6 | Not Available | Not Available |
| 1976 March | 0.569 | 0.594 | Not Available | Not Available |
| 1976 April | 0.567 | 0.592 | Not Available | Not Available |
| 1976 May | 0.576 | 0.6 | Not Available | Not Available |
| 1976 June | 0.592 | 0.616 | Not Available | Not Available |
| 1976 July | 0.599 | 0.623 | Not Available | Not Available |
| 1976 August | 0.603 | 0.628 | Not Available | Not Available |
| 1976 September | 0.604 | 0.63 | Not Available | Not Available |
| 1976 October | 0.603 | 0.629 | Not Available | Not Available |
| 1976 November | 0.602 | 0.629 | Not Available | Not Available |
| 1976 December | 0.6 | 0.626 | Not Available | Not Available |
| 1976 Average | 0.59 | 0.614 | Not Available | Not Available |
| 1977 January | 0.6 | 0.627 | Not Available | Not Available |
| 1977 February | 0.607 | 0.637 | Not Available | Not Available |
| 1977 March | 0.612 | 0.643 | Not Available | Not Available |
| 1977 April | 0.619 | 0.651 | Not Available | Not Available |
| 1977 May | 0.626 | 0.659 | Not Available | Not Available |
| 1977 June | 0.63 | 0.665 | Not Available | Not Available |
| 1977 July | 0.631 | 0.667 | Not Available | Not Available |
| 1977 August | 0.63 | 0.667 | Not Available | Not Available |
| 1977 September | 0.629 | 0.666 | Not Available | Not Available |
| 1977 October | 0.627 | 0.665 | Not Available | Not Available |
| 1977 November | 0.626 | 0.664 | Not Available | Not Available |
| 1977 December | 0.627 | 0.665 | Not Available | Not Available |
| 1977 Average | 0.622 | 0.656 | Not Available | Not Available |
| 1978 January | 0.607 | 0.648 | Not Available | 0.631 |
| 1978 February | 0.605 | 0.647 | Not Available | 0.629 |
| 1978 March | 0.604 | 0.647 | Not Available | 0.629 |
| 1978 April | 0.606 | 0.649 | Not Available | 0.631 |
| 1978 May | 0.611 | 0.655 | Not Available | 0.637 |
| 1978 June | 0.62 | 0.663 | Not Available | 0.645 |
| 1978 July | 0.629 | 0.674 | Not Available | 0.655 |
| 1978 August | 0.638 | 0.682 | Not Available | 0.663 |
| 1978 September | 0.644 | 0.688 | Not Available | 0.669 |
| 1978 October | 0.645 | 0.69 | Not Available | 0.671 |
| 1978 November | 0.65 | 0.695 | Not Available | 0.676 |
| 1978 December | 0.659 | 0.705 | Not Available | 0.685 |
| 1978 Average | 0.626 | 0.67 | Not Available | 0.652 |
| 1979 January | 0.668 | 0.716 | Not Available | 0.695 |
| 1979 February | 0.681 | 0.73 | Not Available | 0.707 |
| 1979 March | 0.706 | 0.755 | Not Available | 0.733 |
| 1979 April | 0.753 | 0.802 | Not Available | 0.78 |
| 1979 May | 0.797 | 0.844 | Not Available | 0.823 |
| 1979 June | 0.856 | 0.901 | Not Available | 0.88 |
| 1979 July | 0.908 | 0.949 | Not Available | 0.93 |
| 1979 August | 0.943 | 0.988 | Not Available | 0.967 |
| 1979 September | 0.973 | 1.02 | Not Available | 0.998 |
| 1979 October | 0.982 | 1.028 | Not Available | 1.006 |
| 1979 November | 0.994 | 1.041 | Not Available | 1.019 |
| 1979 December | 1.018 | 1.065 | Not Available | 1.042 |
| 1979 Average | 0.857 | 0.903 | Not Available | 0.882 |
| 1980 January | 1.086 | 1.131 | Not Available | 1.11 |
| 1980 February | 1.159 | 1.207 | Not Available | 1.186 |
| 1980 March | 1.202 | 1.252 | Not Available | 1.23 |
| 1980 April | 1.212 | 1.264 | Not Available | 1.242 |
| 1980 May | 1.215 | 1.266 | Not Available | 1.244 |
| 1980 June | 1.217 | 1.269 | Not Available | 1.246 |
| 1980 July | 1.216 | 1.271 | Not Available | 1.247 |
| 1980 August | 1.21 | 1.267 | Not Available | 1.243 |
| 1980 September | 1.197 | 1.257 | Not Available | 1.231 |
| 1980 October | 1.188 | 1.25 | Not Available | 1.223 |
| 1980 November | 1.188 | 1.25 | Not Available | 1.222 |
| 1980 December | 1.197 | 1.258 | Not Available | 1.231 |
| 1980 Average | 1.191 | 1.245 | Not Available | 1.221 |
| 1981 January | 1.238 | 1.298 | Not Available | 1.269 |
| 1981 February | 1.321 | 1.382 | Not Available | 1.353 |
| 1981 March | 1.352 | 1.417 | Not Available | 1.388 |
| 1981 April | 1.344 | 1.412 | Not Available | 1.381 |
| 1981 May | 1.333 | 1.4 | Not Available | 1.37 |
| 1981 June | 1.324 | 1.391 | Not Available | 1.362 |
| 1981 July | 1.315 | 1.382 | Not Available | 1.353 |
| 1981 August | 1.31 | 1.376 | Not Available | 1.348 |
| 1981 September | 1.305 | 1.376 | 1.471 | 1.358 |
| 1981 October | 1.299 | 1.371 | 1.47 | 1.353 |
| 1981 November | 1.297 | 1.369 | 1.47 | 1.351 |
| 1981 December | 1.293 | 1.365 | 1.468 | 1.348 |
| 1981 Average | 1.311 | 1.378 | 1.47 | 1.353 |
| 1982 January | 1.285 | 1.358 | 1.466 | 1.341 |
| 1982 February | 1.26 | 1.334 | 1.448 | 1.318 |
| 1982 March | 1.206 | 1.284 | 1.408 | 1.268 |
| 1982 April | 1.148 | 1.225 | 1.351 | 1.21 |
| 1982 May | 1.166 | 1.237 | 1.355 | 1.224 |
| 1982 June | 1.242 | 1.309 | 1.418 | 1.296 |
| 1982 July | 1.263 | 1.331 | 1.443 | 1.318 |
| 1982 August | 1.254 | 1.323 | 1.439 | 1.31 |
| 1982 September | 1.236 | 1.307 | 1.429 | 1.292 |
| 1982 October | 1.219 | 1.295 | 1.421 | 1.28 |
| 1982 November | 1.207 | 1.283 | 1.412 | 1.268 |
| 1982 December | 1.181 | 1.26 | 1.394 | 1.244 |
| 1982 Average | 1.222 | 1.296 | 1.415 | 1.281 |
| 1983 January | 1.15 | 1.23 | 1.376 | 1.214 |
| 1983 February | 1.099 | 1.187 | 1.338 | 1.17 |
| 1983 March | 1.064 | 1.152 | 1.308 | 1.135 |
| 1983 April | 1.131 | 1.215 | 1.36 | 1.198 |
| 1983 May | 1.177 | 1.259 | 1.397 | 1.243 |
| 1983 June | 1.197 | 1.277 | 1.411 | 1.261 |
| 1983 July | 1.207 | 1.288 | 1.421 | 1.272 |
| 1983 August | 1.203 | 1.285 | 1.419 | 1.269 |
| 1983 September | 1.189 | 1.274 | 1.41 | 1.257 |
| 1983 October | 1.172 | 1.255 | 1.395 | 1.239 |
| 1983 November | 1.156 | 1.241 | 1.384 | 1.224 |
| 1983 December | 1.146 | 1.231 | 1.376 | 1.215 |
| 1983 Average | 1.157 | 1.241 | 1.383 | 1.225 |
| 1984 January | 1.131 | 1.216 | 1.369 | 1.2 |
| 1984 February | 1.125 | 1.209 | 1.361 | 1.193 |
| 1984 March | 1.125 | 1.21 | 1.362 | 1.194 |
| 1984 April | 1.145 | 1.227 | 1.375 | 1.211 |
| 1984 May | 1.154 | 1.236 | 1.38 | 1.221 |
| 1984 June | 1.147 | 1.229 | 1.377 | 1.214 |
| 1984 July | 1.129 | 1.212 | 1.37 | 1.197 |
| 1984 August | 1.116 | 1.196 | 1.355 | 1.184 |
| 1984 September | 1.12 | 1.203 | 1.36 | 1.189 |
| 1984 October | 1.127 | 1.209 | 1.365 | 1.195 |
| 1984 November | 1.124 | 1.207 | 1.364 | 1.193 |
| 1984 December | 1.109 | 1.193 | 1.354 | 1.179 |
| 1984 Average | 1.129 | 1.212 | 1.366 | 1.198 |
| 1985 January | 1.06 | 1.148 | 1.304 | 1.145 |
| 1985 February | 1.041 | 1.131 | 1.29 | 1.128 |
| 1985 March | 1.071 | 1.159 | 1.31 | 1.155 |
| 1985 April | 1.119 | 1.205 | 1.34 | 1.199 |
| 1985 May | 1.144 | 1.231 | 1.36 | 1.223 |
| 1985 June | 1.153 | 1.241 | 1.371 | 1.233 |
| 1985 July | 1.154 | 1.242 | 1.367 | 1.233 |
| 1985 August | 1.143 | 1.229 | 1.359 | 1.222 |
| 1985 September | 1.129 | 1.216 | 1.349 | 1.209 |
| 1985 October | 1.117 | 1.204 | 1.342 | 1.198 |
| 1985 November | 1.123 | 1.207 | 1.339 | 1.201 |
| 1985 December | 1.123 | 1.208 | 1.344 | 1.203 |
| 1985 Average | 1.115 | 1.202 | 1.34 | 1.196 |
| 1986 January | 1.107 | 1.194 | 1.336 | 1.19 |
| 1986 February | 1.034 | 1.12 | 1.282 | 1.119 |
| 1986 March | 0.894 | 0.981 | 1.16 | 0.983 |
| 1986 April | 0.815 | 0.888 | 1.061 | 0.895 |
| 1986 May | 0.852 | 0.923 | 1.075 | 0.927 |
| 1986 June | 0.885 | 0.955 | 1.1 | 0.958 |
| 1986 July | 0.822 | 0.89 | 1.045 | 0.895 |
| 1986 August | 0.778 | 0.843 | 0.999 | 0.848 |
| 1986 September | 0.797 | 0.86 | 1.01 | 0.864 |
| 1986 October | 0.771 | 0.831 | 0.987 | 0.837 |
| 1986 November | 0.762 | 0.821 | 0.98 | 0.827 |
| 1986 December | 0.764 | 0.823 | 0.984 | 0.83 |
| 1986 Average | 0.857 | 0.927 | 1.085 | 0.931 |
| 1987 January | 0.806 | 0.862 | 1.007 | 0.868 |
| 1987 February | 0.848 | 0.905 | 1.047 | 0.911 |
| 1987 March | 0.856 | 0.912 | 1.052 | 0.918 |
| 1987 April | 0.879 | 0.934 | 1.073 | 0.94 |
| 1987 May | 0.888 | 0.941 | 1.079 | 0.948 |
| 1987 June | 0.906 | 0.958 | 1.098 | 0.966 |
| 1987 July | 0.921 | 0.971 | 1.115 | 0.98 |
| 1987 August | 0.946 | 0.995 | 1.139 | 1.004 |
| 1987 September | 0.94 | 0.99 | 1.136 | 1 |
| 1987 October | 0.931 | 0.976 | 1.128 | 0.988 |
| 1987 November | 0.928 | 0.976 | 1.125 | 0.987 |
| 1987 December | 0.912 | 0.961 | 1.119 | 0.975 |
| 1987 Average | 0.897 | 0.948 | 1.093 | 0.957 |
| 1988 January | 0.881 | 0.933 | 1.095 | 0.947 |
| 1988 February | 0.859 | 0.913 | 1.082 | 0.928 |
| 1988 March | 0.85 | 0.904 | 1.074 | 0.92 |
| 1988 April | 0.883 | 0.93 | 1.088 | 0.946 |
| 1988 May | 0.911 | 0.955 | 1.105 | 0.97 |
| 1988 June | 0.91 | 0.955 | 1.111 | 0.971 |
| 1988 July | 0.923 | 0.967 | 1.123 | 0.984 |
| 1988 August | 0.945 | 0.987 | 1.138 | 1.004 |
| 1988 September | 0.933 | 0.974 | 1.13 | 0.992 |
| 1988 October | 0.91 | 0.957 | 1.119 | 0.976 |
| 1988 November | 0.904 | 0.949 | 1.116 | 0.972 |
| 1988 December | 0.885 | 0.93 | 1.101 | 0.953 |
| 1988 Average | 0.899 | 0.946 | 1.107 | 0.963 |
| 1989 January | 0.876 | 0.918 | 1.091 | 0.944 |
| 1989 February | 0.886 | 0.926 | 1.1 | 0.955 |
| 1989 March | 0.907 | 0.94 | 1.115 | 0.974 |
| 1989 April | 1.047 | 1.065 | 1.221 | 1.098 |
| 1989 May | 1.098 | 1.119 | 1.278 | 1.152 |
| 1989 June | 1.093 | 1.114 | 1.278 | 1.15 |
| 1989 July | 1.075 | 1.092 | 1.264 | 1.132 |
| 1989 August | 1.034 | 1.057 | 1.233 | 1.096 |
| 1989 September | 1.007 | 1.029 | 1.213 | 1.073 |
| 1989 October | 1.001 | 1.027 | 1.209 | 1.071 |
| 1989 November | 0.975 | 0.999 | 1.187 | 1.046 |
| 1989 December | 0.961 | 0.98 | 1.17 | 1.03 |
| 1989 Average | 0.998 | 1.021 | 1.197 | 1.06 |
| 1990 January | 1.006 | 1.042 | 1.23 | 1.09 |
| 1990 February | 1.011 | 1.037 | 1.227 | 1.086 |
| 1990 March | 0.999 | 1.023 | 1.218 | 1.076 |
| 1990 April | 1.027 | 1.044 | 1.233 | 1.096 |
| 1990 May | 1.044 | 1.061 | 1.248 | 1.114 |
| 1990 June | 1.077 | 1.088 | 1.271 | 1.14 |
| 1990 July | 1.089 | 1.084 | 1.272 | 1.139 |
| 1990 August | 1.198 | 1.19 | 1.369 | 1.246 |
| 1990 September | 1.297 | 1.294 | 1.467 | 1.347 |
| 1990 October | 1.354 | 1.378 | 1.554 | 1.431 |
| 1990 November | 1.351 | 1.377 | 1.559 | 1.432 |
| 1990 December | 1.335 | 1.354 | 1.537 | 1.41 |
| 1990 Average | 1.149 | 1.164 | 1.349 | 1.217 |
| 1991 January | 1.246 | 1.247 | 1.431 | 1.304 |
| 1991 February | 1.137 | 1.143 | 1.321 | 1.198 |
| 1991 March | 1.047 | 1.082 | 1.264 | 1.138 |
| 1991 April | 1.062 | 1.104 | 1.281 | 1.159 |
| 1991 May | Not Available | 1.156 | 1.331 | 1.209 |
| 1991 June | Not Available | 1.16 | 1.338 | 1.214 |
| 1991 July | Not Available | 1.127 | 1.313 | 1.185 |
| 1991 August | Not Available | 1.14 | 1.318 | 1.196 |
| 1991 September | Not Available | 1.143 | 1.324 | 1.199 |
| 1991 October | Not Available | 1.122 | 1.307 | 1.18 |
| 1991 November | Not Available | 1.134 | 1.318 | 1.193 |
| 1991 December | Not Available | 1.123 | 1.309 | 1.182 |
| 1991 Average | Not Available | 1.14 | 1.321 | 1.196 |
| 1992 January | Not Available | 1.073 | 1.267 | 1.135 |
| 1992 February | Not Available | 1.054 | 1.248 | 1.117 |
| 1992 March | Not Available | 1.058 | 1.25 | 1.122 |
| 1992 April | Not Available | 1.079 | 1.268 | 1.143 |
| 1992 May | Not Available | 1.136 | 1.317 | 1.197 |
| 1992 June | Not Available | 1.179 | 1.359 | 1.239 |
| 1992 July | Not Available | 1.175 | 1.363 | 1.238 |
| 1992 August | Not Available | 1.158 | 1.348 | 1.221 |
| 1992 September | Not Available | 1.158 | 1.346 | 1.222 |
| 1992 October | Not Available | 1.154 | 1.345 | 1.219 |
| 1992 November | Not Available | 1.159 | 1.351 | 1.223 |
| 1992 December | Not Available | 1.136 | 1.33 | 1.201 |
| 1992 Average | Not Available | 1.127 | 1.316 | 1.19 |
| 1993 January | Not Available | 1.117 | 1.313 | 1.182 |
| 1993 February | Not Available | 1.108 | 1.301 | 1.172 |
| 1993 March | Not Available | 1.098 | 1.294 | 1.163 |
| 1993 April | Not Available | 1.112 | 1.304 | 1.175 |
| 1993 May | Not Available | 1.129 | 1.319 | 1.193 |
| 1993 June | Not Available | 1.13 | 1.321 | 1.194 |
| 1993 July | Not Available | 1.109 | 1.305 | 1.174 |
| 1993 August | Not Available | 1.097 | 1.294 | 1.163 |
| 1993 September | Not Available | 1.085 | 1.282 | 1.151 |
| 1993 October | Not Available | 1.127 | 1.323 | 1.193 |
| 1993 November | Not Available | 1.113 | 1.305 | 1.178 |
| 1993 December | Not Available | 1.07 | 1.268 | 1.136 |
| 1993 Average | Not Available | 1.108 | 1.302 | 1.173 |
| 1994 January | Not Available | 1.043 | 1.24 | 1.109 |
| 1994 February | Not Available | 1.051 | 1.245 | 1.114 |
| 1994 March | Not Available | 1.045 | 1.243 | 1.109 |
| 1994 April | Not Available | 1.064 | 1.26 | 1.128 |
| 1994 May | Not Available | 1.08 | 1.274 | 1.143 |
| 1994 June | Not Available | 1.106 | 1.3 | 1.167 |
| 1994 July | Not Available | 1.136 | 1.327 | 1.199 |
| 1994 August | Not Available | 1.182 | 1.367 | 1.243 |
| 1994 September | Not Available | 1.177 | 1.364 | 1.237 |
| 1994 October | Not Available | 1.152 | 1.345 | 1.212 |
| 1994 November | Not Available | 1.163 | 1.354 | 1.222 |
| 1994 December | Not Available | 1.143 | 1.337 | 1.203 |
| 1994 Average | Not Available | 1.112 | 1.305 | 1.174 |
| 1995 January | Not Available | 1.129 | 1.324 | 1.19 |
| 1995 February | Not Available | 1.12 | 1.316 | 1.181 |
| 1995 March | Not Available | 1.115 | 1.306 | 1.173 |
| 1995 April | Not Available | 1.14 | 1.325 | 1.197 |
| 1995 May | Not Available | 1.2 | 1.383 | 1.256 |
| 1995 June | Not Available | 1.226 | 1.411 | 1.281 |
| 1995 July | Not Available | 1.195 | 1.384 | 1.252 |
| 1995 August | Not Available | 1.164 | 1.352 | 1.222 |
| 1995 September | Not Available | 1.148 | 1.332 | 1.206 |
| 1995 October | Not Available | 1.127 | 1.315 | 1.185 |
| 1995 November | Not Available | 1.101 | 1.292 | 1.161 |
| 1995 December | Not Available | 1.101 | 1.29 | 1.16 |
| 1995 Average | Not Available | 1.147 | 1.336 | 1.205 |
| 1996 January | Not Available | 1.129 | 1.317 | 1.186 |
| 1996 February | Not Available | 1.124 | 1.311 | 1.181 |
| 1996 March | Not Available | 1.162 | 1.348 | 1.219 |
| 1996 April | Not Available | 1.251 | 1.431 | 1.305 |
| 1996 May | Not Available | 1.323 | 1.507 | 1.378 |
| 1996 June | Not Available | 1.299 | 1.481 | 1.354 |
| 1996 July | Not Available | 1.272 | 1.453 | 1.328 |
| 1996 August | Not Available | 1.24 | 1.421 | 1.298 |
| 1996 September | Not Available | 1.234 | 1.417 | 1.293 |
| 1996 October | Not Available | 1.227 | 1.408 | 1.287 |
| 1996 November | Not Available | 1.25 | 1.428 | 1.308 |
| 1996 December | Not Available | 1.26 | 1.438 | 1.318 |
| 1996 Average | Not Available | 1.231 | 1.413 | 1.288 |
| 1997 January | Not Available | 1.261 | 1.441 | 1.318 |
| 1997 February | Not Available | 1.255 | 1.434 | 1.312 |
| 1997 March | Not Available | 1.235 | 1.415 | 1.293 |
| 1997 April | Not Available | 1.231 | 1.413 | 1.288 |
| 1997 May | Not Available | 1.226 | 1.409 | 1.284 |
| 1997 June | Not Available | 1.229 | 1.411 | 1.286 |
| 1997 July | Not Available | 1.205 | 1.388 | 1.263 |
| 1997 August | Not Available | 1.253 | 1.433 | 1.31 |
| 1997 September | Not Available | 1.277 | 1.458 | 1.334 |
| 1997 October | Not Available | 1.242 | 1.426 | 1.3 |
| 1997 November | Not Available | 1.213 | 1.397 | 1.271 |
| 1997 December | Not Available | 1.177 | 1.363 | 1.236 |
| 1997 Average | Not Available | 1.234 | 1.416 | 1.291 |
| 1998 January | Not Available | 1.131 | 1.319 | 1.186 |
| 1998 February | Not Available | 1.082 | 1.271 | 1.137 |
| 1998 March | Not Available | 1.041 | 1.229 | 1.097 |
| 1998 April | Not Available | 1.052 | 1.237 | 1.106 |
| 1998 May | Not Available | 1.092 | 1.275 | 1.146 |
| 1998 June | Not Available | 1.094 | 1.279 | 1.148 |
| 1998 July | Not Available | 1.079 | 1.268 | 1.134 |
| 1998 August | Not Available | 1.052 | 1.244 | 1.108 |
| 1998 September | Not Available | 1.033 | 1.23 | 1.091 |
| 1998 October | Not Available | 1.042 | 1.236 | 1.099 |
| 1998 November | Not Available | 1.028 | 1.225 | 1.086 |
| 1998 December | Not Available | 0.986 | 1.187 | 1.046 |
| 1998 Average | Not Available | 1.059 | 1.25 | 1.115 |
| 1999 January | Not Available | 0.972 | 1.171 | 1.031 |
| 1999 February | Not Available | 0.955 | 1.155 | 1.014 |
| 1999 March | Not Available | 0.991 | 1.186 | 1.048 |
| 1999 April | Not Available | 1.177 | 1.367 | 1.232 |
| 1999 May | Not Available | 1.178 | 1.37 | 1.233 |
| 1999 June | Not Available | 1.148 | 1.339 | 1.204 |
| 1999 July | Not Available | 1.189 | 1.378 | 1.244 |
| 1999 August | Not Available | 1.255 | 1.441 | 1.309 |
| 1999 September | Not Available | 1.28 | 1.468 | 1.334 |
| 1999 October | Not Available | 1.274 | 1.464 | 1.329 |
| 1999 November | Not Available | 1.264 | 1.454 | 1.319 |
| 1999 December | Not Available | 1.298 | 1.486 | 1.353 |
| 1999 Average | Not Available | 1.165 | 1.357 | 1.221 |
| 2000 January | Not Available | 1.301 | 1.486 | 1.356 |
| 2000 February | Not Available | 1.369 | 1.551 | 1.422 |
| 2000 March | Not Available | 1.541 | 1.723 | 1.594 |
| 2000 April | Not Available | 1.506 | 1.698 | 1.561 |
| 2000 May | Not Available | 1.498 | 1.682 | 1.552 |
| 2000 June | Not Available | 1.617 | 1.786 | 1.666 |
| 2000 July | Not Available | 1.593 | 1.773 | 1.642 |
| 2000 August | Not Available | 1.51 | 1.689 | 1.559 |
| 2000 September | Not Available | 1.582 | 1.764 | 1.635 |
| 2000 October | Not Available | 1.559 | 1.744 | 1.613 |
| 2000 November | Not Available | 1.555 | 1.738 | 1.608 |
| 2000 December | Not Available | 1.489 | 1.679 | 1.544 |
| 2000 Average | Not Available | 1.51 | 1.693 | 1.563 |
| 2001 January | Not Available | 1.472 | 1.657 | 1.525 |
| 2001 February | Not Available | 1.484 | 1.671 | 1.538 |
| 2001 March | Not Available | 1.447 | 1.638 | 1.503 |
| 2001 April | Not Available | 1.564 | 1.748 | 1.617 |
| 2001 May | Not Available | 1.729 | 1.934 | 1.812 |
| 2001 June | Not Available | 1.64 | 1.881 | 1.731 |
| 2001 July | Not Available | 1.482 | 1.695 | 1.565 |
| 2001 August | Not Available | 1.427 | 1.636 | 1.509 |
| 2001 September | Not Available | 1.531 | 1.726 | 1.609 |
| 2001 October | Not Available | 1.362 | 1.56 | 1.442 |
| 2001 November | Not Available | 1.263 | 1.427 | 1.324 |
| 2001 December | Not Available | 1.131 | 1.312 | 1.2 |
| 2001 Average | Not Available | 1.461 | 1.657 | 1.531 |
| 2002 January | Not Available | 1.139 | 1.323 | 1.209 |
| 2002 February | Not Available | 1.13 | 1.33 | 1.21 |
| 2002 March | Not Available | 1.241 | 1.45 | 1.324 |
| 2002 April | Not Available | 1.407 | 1.622 | 1.493 |
| 2002 May | Not Available | 1.421 | 1.625 | 1.508 |
| 2002 June | Not Available | 1.404 | 1.606 | 1.489 |
| 2002 July | Not Available | 1.412 | 1.607 | 1.496 |
| 2002 August | Not Available | 1.423 | 1.62 | 1.508 |
| 2002 September | Not Available | 1.422 | 1.619 | 1.507 |
| 2002 October | Not Available | 1.449 | 1.643 | 1.535 |
| 2002 November | Not Available | 1.448 | 1.643 | 1.534 |
| 2002 December | Not Available | 1.394 | 1.589 | 1.477 |
| 2002 Average | Not Available | 1.358 | 1.556 | 1.441 |
| 2003 January | Not Available | 1.473 | 1.666 | 1.557 |
| 2003 February | Not Available | 1.641 | 1.828 | 1.686 |
| 2003 March | Not Available | 1.748 | 1.924 | 1.791 |
| 2003 April | Not Available | 1.659 | 1.846 | 1.704 |
| 2003 May | Not Available | 1.542 | 1.729 | 1.587 |
| 2003 June | Not Available | 1.514 | 1.7 | 1.558 |
| 2003 July | Not Available | 1.524 | 1.71 | 1.567 |
| 2003 August | Not Available | 1.628 | 1.808 | 1.671 |
| 2003 September | Not Available | 1.728 | 1.911 | 1.771 |
| 2003 October | Not Available | 1.603 | 1.789 | 1.646 |
| 2003 November | Not Available | 1.535 | 1.724 | 1.578 |
| 2003 December | Not Available | 1.494 | 1.686 | 1.538 |
| 2003 Average | Not Available | 1.591 | 1.777 | 1.638 |
| 2004 January | Not Available | 1.592 | 1.779 | 1.635 |
| 2004 February | Not Available | 1.672 | 1.858 | 1.715 |
| 2004 March | Not Available | 1.766 | 1.949 | 1.809 |
| 2004 April | Not Available | 1.833 | 2.012 | 1.875 |
| 2004 May | Not Available | 2.009 | 2.186 | 2.05 |
| 2004 June | Not Available | 2.041 | 2.225 | 2.083 |
| 2004 July | Not Available | 1.939 | 2.13 | 1.982 |
| 2004 August | Not Available | 1.898 | 2.091 | 1.941 |
| 2004 September | Not Available | 1.891 | 2.082 | 1.934 |
| 2004 October | Not Available | 2.029 | 2.215 | 2.072 |
| 2004 November | Not Available | 2.01 | 2.203 | 2.053 |
| 2004 December | Not Available | 1.882 | 2.08 | 1.926 |
| 2004 Average | Not Available | 1.88 | 2.068 | 1.923 |
| 2005 January | Not Available | 1.823 | 2.017 | 1.866 |
| 2005 February | Not Available | 1.918 | 2.105 | 1.96 |
| 2005 March | Not Available | 2.065 | 2.251 | 2.107 |
| 2005 April | Not Available | 2.283 | 2.468 | 2.325 |
| 2005 May | Not Available | 2.216 | 2.403 | 2.257 |
| 2005 June | Not Available | 2.176 | 2.365 | 2.218 |
| 2005 July | Not Available | 2.316 | 2.502 | 2.357 |
| 2005 August | Not Available | 2.506 | 2.701 | 2.548 |
| 2005 September | Not Available | 2.927 | 3.13 | 2.969 |
| 2005 October | Not Available | 2.785 | 3.001 | 2.83 |
| 2005 November | Not Available | 2.343 | 2.56 | 2.387 |
| 2005 December | Not Available | 2.186 | 2.393 | 2.23 |
| 2005 Average | Not Available | 2.295 | 2.491 | 2.338 |
| 2006 January | Not Available | 2.315 | 2.521 | 2.359 |
| 2006 February | Not Available | 2.31 | 2.519 | 2.354 |
| 2006 March | Not Available | 2.401 | 2.603 | 2.444 |
| 2006 April | Not Available | 2.757 | 2.967 | 2.801 |
| 2006 May | Not Available | 2.947 | 3.169 | 2.993 |
| 2006 June | Not Available | 2.917 | 3.139 | 2.963 |
| 2006 July | Not Available | 2.999 | 3.219 | 3.046 |
| 2006 August | Not Available | 2.985 | 3.207 | 3.033 |
| 2006 September | Not Available | 2.589 | 2.819 | 2.637 |
| 2006 October | Not Available | 2.272 | 2.493 | 2.319 |
| 2006 November | Not Available | 2.241 | 2.459 | 2.287 |
| 2006 December | Not Available | 2.334 | 2.55 | 2.38 |
| 2006 Average | Not Available | 2.589 | 2.805 | 2.635 |
| 2007 January | Not Available | 2.274 | 2.501 | 2.321 |
| 2007 February | Not Available | 2.285 | 2.509 | 2.333 |
| 2007 March | Not Available | 2.592 | 2.818 | 2.639 |
| 2007 April | Not Available | 2.86 | 3.093 | 2.909 |
| 2007 May | Not Available | 3.13 | 3.348 | 3.176 |
| 2007 June | Not Available | 3.052 | 3.281 | 3.1 |
| 2007 July | Not Available | 2.961 | 3.2 | 3.013 |
| 2007 August | Not Available | 2.782 | 3.018 | 2.833 |
| 2007 September | Not Available | 2.789 | 3.021 | 2.839 |
| 2007 October | Not Available | 2.793 | 3.037 | 2.843 |
| 2007 November | Not Available | 3.069 | 3.307 | 3.118 |
| 2007 December | Not Available | 3.02 | 3.264 | 3.069 |
| 2007 Average | Not Available | 2.801 | 3.033 | 2.849 |
| 2008 January | Not Available | 3.047 | 3.291 | 3.096 |
| 2008 February | Not Available | 3.033 | 3.272 | 3.083 |
| 2008 March | Not Available | 3.258 | 3.502 | 3.307 |
| 2008 April | Not Available | 3.441 | 3.69 | 3.491 |
| 2008 May | Not Available | 3.764 | 4.003 | 3.813 |
| 2008 June | Not Available | 4.065 | 4.319 | 4.115 |
| 2008 July | Not Available | 4.09 | 4.35 | 4.142 |
| 2008 August | Not Available | 3.786 | 4.045 | 3.838 |
| 2008 September | Not Available | 3.698 | 3.94 | 3.749 |
| 2008 October | Not Available | 3.173 | 3.432 | 3.225 |
| 2008 November | Not Available | 2.151 | 2.433 | 2.208 |
| 2008 December | Not Available | 1.689 | 1.951 | 1.742 |
| 2008 Average | Not Available | 3.266 | 3.519 | 3.317 |
| 2009 January | Not Available | 1.787 | 2.036 | 1.838 |
| 2009 February | Not Available | 1.928 | 2.182 | 1.979 |
| 2009 March | Not Available | 1.949 | 2.197 | 2 |
| 2009 April | Not Available | 2.056 | 2.309 | 2.107 |
| 2009 May | Not Available | 2.265 | 2.511 | 2.314 |
| 2009 June | Not Available | 2.631 | 2.883 | 2.681 |
| 2009 July | Not Available | 2.543 | 2.806 | 2.594 |
| 2009 August | Not Available | 2.627 | 2.887 | 2.677 |
| 2009 September | Not Available | 2.574 | 2.845 | 2.626 |
| 2009 October | Not Available | 2.561 | 2.826 | 2.613 |
| 2009 November | Not Available | 2.66 | 2.917 | 2.709 |
| 2009 December | Not Available | 2.621 | 2.882 | 2.671 |
| 2009 Average | Not Available | 2.35 | 2.607 | 2.401 |
| 2010 January | Not Available | 2.731 | 2.987 | 2.779 |
| 2010 February | Not Available | 2.659 | 2.922 | 2.709 |
| 2010 March | Not Available | 2.78 | 3.035 | 2.829 |
| 2010 April | Not Available | 2.858 | 3.113 | 2.906 |
| 2010 May | Not Available | 2.869 | 3.124 | 2.915 |
| 2010 June | Not Available | 2.736 | 3 | 2.783 |
| 2010 July | Not Available | 2.736 | 2.997 | 2.783 |
| 2010 August | Not Available | 2.745 | 3.015 | 2.795 |
| 2010 September | Not Available | 2.704 | 2.968 | 2.754 |
| 2010 October | Not Available | 2.795 | 3.055 | 2.843 |
| 2010 November | Not Available | 2.852 | 3.109 | 2.899 |
| 2010 December | Not Available | 2.985 | 3.234 | 3.031 |
| 2010 Average | Not Available | 2.788 | 3.047 | 2.836 |
| 2011 January | Not Available | 3.091 | 3.345 | 3.139 |
| 2011 February | Not Available | 3.167 | 3.424 | 3.215 |
| 2011 March | Not Available | 3.546 | 3.807 | 3.594 |
| 2011 April | Not Available | 3.816 | 4.074 | 3.863 |