This database provides urban consumer prices for energy goods and services, as measured by changes in the Consumer Price Index (CPI-U).  See Measuring Price Change for commodity definitions.  Some data are adjusted for seasonal variations, although most are not.  (Seasonal variations typically occur for goods and services such as agriculture, tourism, energy, and others in which seasonal demand has a substantial impact on prices.)  A limited number of measures are available starting in 1935. Most are available for shorter periods. 

Data are not available for all combinations of items, areas, and time periods.  Data are presented as indexes or percentage changes for the preceding 12-month period.  Most indexes have a base period of 1982-1984 = 100.  For additional details on categories and methodology, see Consumer Price Index.  For background on calculating the percentage change bases on index values, see Calculating Consumer Price Changes.