Korea's core inflation hit 3.4%. A phone bill from last August did most of it.

Korean consumer prices rose 3.1% in the year to August 2026, and the core index — the one that strips out food and energy — rose 3.4%. Core has not outrun headline by that margin at any point this year. The single biggest reason is that SK Telecom halved its customers’ phone bills in August 2025.

The mobile discount that became an inflation print

After a data breach exposed subscriber data in April 2025, SK Telecom gave every eligible customer a 50% discount on their August 2025 bill, part of a compensation package the company put at ₩500bn covering roughly 24 million users on its own network and on MVNOs riding it.

The statistics office recorded that faithfully. The communication expenditure group fell 13.3% in a single month, taking its index from 101.35 in July 2025 to 87.87 in August.

Twelve months later, the discount is gone and the comparison is against that hole. Communication printed 102.48 in August 2026 — up 16.6% year on year, against 0.7% a month earlier.

Strip it out and inflation is falling

Rebuild the index without communication and both months change character. Excluding that group, prices rose 2.9% in the year to July and 2.6% in the year to August — a deceleration, not the acceleration the published figures show.

The core measure moved further than headline for a mechanical reason. Communication is neither food nor energy, so it never leaves the core basket — and that basket is smaller than the full one, so the same 14.61-point jump lands with more force.

This unwinds. The discount applied to one billing month, and by July 2026 the communication index had returned to roughly where it was two years earlier. Assuming September 2025 was not similarly depressed, the September 2026 release should shed most of the distortion.

What is actually getting more expensive

The rest of the table is less dramatic and more useful. Transport rose 7.2% year on year, driven by petroleum, though it fell 0.1% on the month. Recreation and culture was up 4.9%, miscellaneous goods and services 4.4%, restaurants and hotels 2.8%.

Food and non-alcoholic beverages went the other way: the index read 128.27 against 128.96 a year earlier, a fall of 0.5%. Groceries in Korea are cheaper than they were last August, for the first time this year — which is not what most households will report, because the categories that grew fastest are the ones people pay monthly and notice.

Housing, water, electricity and gas rose 1.9%, and education 1.3%.

The Bank of Korea already decided

Governor and board had made their call before this print. On 27 August the Monetary Policy Board raised the base rate to 3.00%, its second consecutive quarter-point move, and published a six-month outlook in which sixteen of twenty-one dots sat above the new level. That decision rested on the composition of price pressure, on housing in the capital region and on household credit — not on an August CPI number nobody had yet seen. The full dot plot and what the board said about it is the better guide to where rates go next.

For borrowers the practical question is unchanged, and it is a question about the mortgage book rather than about August’s index. Korean households have been switching into floating-rate mortgages just as the tightening cycle began, which is the transmission channel that matters if the dots are right.

Anyone building a forecast off this month’s core reading is forecasting a telecoms apology.

Figures current as of 2 September 2026, sourced to the outlets and data portals listed below.