The Consumer Price Index dropped by 0.7 percent in January 2015 on a seasonally adjusted basis. The all items index decrease was driven mostly by a decrease in gas prices, which fell 18.7 percent in January. In fact, if gas had not changed prices in January, the all items index would have increased by 0.1 percent for the month.

Over the year, the all items index fell by 0.1 percent. This marks the first time prices have fallen over the year since 2009.

For the full report on CPI, read the BLS' latest news release.