The opinions expressed here are those of the authors.

By Anna Szymanski

June 26 (Reuters) - Every Friday, Reuters Open Interest (ROI) distills the financial week into five key charts, spotlighting the major trends, surprises and overlooked moves that defined the past five days.

1. WHAT GOES UP ...

ANNA SZYMANSKI, ROI Editor in Charge: South Korea's KOSPI may be down roughly 7% this week, but the chip-heavy index still managed a monstrous 66% gain for the quarter, the best since 1998, and has roughly doubled since the start of the year. Will this week's ructions prove to be a turning point or a speed bump? Recent history suggests the latter.

2. GRID UNDER HEAT

GAVIN MAGUIRE, ROI Global Energy Transition Columnist: Britain's power prices are being closely tracked as record high temperatures strain the country's grids and disrupt daily life. Wholesale prices have jumped to twice their average for 2026 so far, as demand for cooling systems surges just as power suppliers are forced to reduce output to avoid outages. To learn more, here's a guide to track the heat wave's impact on power systems throughout the UK and Europe.

3. HOW STICKY IS STICKY?

MIKE DOLAN, ROI Finance & Markets Columnist: U.S. inflation picked up again in May and remains stubbornly above the Federal Reserve's target. Even new Federal Reserve boss Kevin Warsh's preferred trimmed-mean measure, which strips out extreme monthly price moves, is edging toward 3%. But with crude prices now back near pre-Iran war levels, June inflation data will be closely watched for signs that underlying price pressures are easing alongside energy costs. To complicate matters, there are growing questions about whether lower prices at the pump could actually make overall inflation worse.

4. RETHINKING THE NORTH SEA

RON BOUSSO, ROI Energy Columnist: The latest bout of political turmoil in Britain comes as energy security has moved front and centre following the Iran war, offering the next prime minister a chance to rethink the country's strategy restricting North Sea oil and gas activity.

5. AFRICA'S MINERAL MUSCLE

ANDY HOME, ROI Metals Columnist: China's imports of cobalt from the Democratic Republic of Congo collapsed after the imposition of export restrictions. This speaks to a broader trend of African countries seeking to reap greater rewards from their critical mineral wealth.

Opinions expressed are those of the authors. They do not reflect the views of Reuters News, which, under the Trust Principles, is committed to integrity, independence, and freedom from bias.