Consumer prices as measured by the Labor Department's Consumer Price Index fell 0.1% in March on a seasonally adjusted basis, putting the index down 0.4% during the past 12 months, the first year-over-year decline in prices since 1955. The index was up 0.4% in February.

The Labor Department on Wednesday morning said both its unadjusted CPI and its core CPI, which excludes food and energy, posted 0.2% increases.

The decline in the seasonally adjusted index was driven by a 3.0% drop in the energy index, which had been up 3.3% in February. All of the component energy indices fell. The food index also fell, by 0.1% for the second consecutive month, putting prices at October 2008 levels. The food at home index, however, dropped 0.4%, also for the second consecutive month.

The Labor Department said that 60% of the 0.2% rise in the core CPI index was driven by an 11.0% spike in the index for tobacco and smoking products as tobacco makers hiked prices across the board in anticipation of significantly higher federal and state taxes on their products at retail. The index for all items less food and energy has risen 1.8% over the past year.

After being virtually unchanged in February, the housing index declined 0.1% in March. The shelter index was virtually unchanged in March. The indices for rent and owners' equivalent rent both rose 0.2%.

For the first three months of 2009, consumer prices increased at a seasonally adjusted annualized rate of 2.2%, compared to a 0.1% increase for all of 2008. The index for energy, which fell 21.3% in 2008, advanced at a 7.9% seasonally adjusted annual rate in the quarter.