The core consumer price index – which excludes fresh foods – increased 4.0% from a year earlier, up from 3.7% in November, according to the internal affairs and communications ministry. Last month’s figure marked the sharpest rise since December 1981.

Prices of electricity increased 21.3%, while grains rose 9.6%.

Last year’s core consumer inflation rate averaged 2.3%.

The statistics come two days after the Bank of Japan kept its ultraloose monetary policy unchanged in its latest monetary policy meeting.

The 4.0% rise in December means that Japan’s core inflation has now surpassed the BOJ’s price stability target of 2% for the ninth consecutive month.

Still, the central bank is sticking to its guns, with governor Haruhiko Kuroda saying it will aim for the sustained and stable realization of its price target in a manner that is accompanied by wage increases.

The BOJ said that core inflation is expected to slow down through the middle of fiscal 2023, which begins in April, partly thanks to the government’s measures to restrain energy prices. The bank projects a core consumer inflation rate of 1.6% for fiscal 2023.

Meanwhile, companies were planning to raise prices of about 7,100 food products between January and April, according to a December survey by research firm Teikoku Databank, which covered 105 major food producers.

The research firm said the higher cost of logistics and labour, as well as the weak yen, are the main factors driving the price hikes.