WASHINGTON (MarketWatch) — Consumer inflation in December saw the biggest monthly drop in six years as gasoline prices tumbled, according to government data released Friday.

U.S. consumer prices fell 0.4% in December, the largest drop since the end of 2008, matching expectations from economists polled by MarketWatch. Energy prices plunged 4.7% in December, the biggest drop since the end of 2008, as gasoline prices fell 9.4%, the U.S. Labor Department reported. Energy prices are expected to drag down headline inflation in coming months as well.

Overall consumer prices grew 0.8% in 2014 — the second smallest calendar-year increase in the last five decades. In addition to gas, TVs, computers and others items saw prices drop last year, while goods such as beef and hotels became pricier.

While low inflation sounds good to consumers, Federal Reserve officials want to make sure that inflation doesn’t get too low. That’s because it’s hard to break the vicious cycle of deflation — a sustained downward price trend that sees consumers delay purchases, weakening the economy.

The “core” reading of inflation, which excludes the volatile categories of food and energy, showed that prices were unchanged in December, compared with a gain of 0.1% in November. Economists had expected core inflation of 0.1%.

Core inflation was 1.6% during 2014.

“With core inflation unlikely to fall much below December’s 1.6%...and headline inflation to rebound to 2.0% early in 2016, the Fed will still raise rates this year,” said Paul Dales, senior U.S. economist at and Capital Economics. “Since lower gasoline prices provide a net boost to activity, core inflation is unlikely to fall much further.”

In December prices rose 0.3% for food and 0.2% for shelter. Apparel prices skidded 1.2%, the biggest drop since 1998, which may have been a reason why retail sales — which reflect both volumes and prices — were so disappointing in December.

Later Friday morning, markets will see a fresh reading on consumer sentiment, which economists follow to get a feel for the direction of consumer spending. The consensus estimate expects that the University of Michigan/Thomson Reuters consumer-sentiment index rose to 95 this month, which would be the highest reading in eight years, from 93.6 at the end of December.

Also Friday, the government reported that inflation-adjusted average hourly earnings rose 0.1% in December. For the year, real average hourly earnings rose 1%.