The Organisation for Economic Co-operation and Development published its March 2026 interim economic outlook on Thursday and the headline number tells the story: global GDP growth has been cut to 2.9% for 2026, down from 3.3% projected in December, with inflation forecasts raised across the board.

The culprit is not complicated. The closure of the Strait of Hormuz, the destruction of energy infrastructure in the Gulf, and the resulting spike in oil prices have created what the OECD calls "a significant adverse supply shock" — economist-speak for an economic catastrophe that nobody can control and everybody has to pay for.

The Damage by Region

The eurozone has been cut to 0.8% growth, down from 1.3% in the December forecast. France is already in its third consecutive month of contraction. Germany is barely above zero. Only Spain, shielded partly by its renewable energy capacity, is growing at anything close to trend.

The United States forecast has been trimmed to 2.0%, down from 2.4%. The American economy is more insulated from the oil shock thanks to domestic production, but higher energy costs are still feeding through to consumers and businesses. The Fed's hawkish stance is adding to the drag.

South Korea took one of the largest single-country downgrades: from 2.1% to 1.7%, reflecting its heavy dependence on imported energy and its exposure to disrupted Asian shipping lanes. Japan was cut to 1.0%. India's forecast was trimmed by 0.3 points.

Inflation: The Sting in the Tail

Perhaps the most alarming number in the report is the inflation revision. Headline inflation in the G20 advanced economies is now projected at 4.0% for 2026 — a full 1.2 percentage points higher than the December forecast. The OECD expects inflation to ease to 2.7% in 2027, but only if energy prices moderate from the second quarter onward.

That is a big "if." Brent crude is averaging $90 per barrel in March and the OECD's baseline assumes a gradual decline to $60 by year-end. If the Hormuz blockade persists, or if the conflict escalates further, those assumptions collapse and the inflation picture gets dramatically worse.

The Central Bank Dilemma

Central banks are caught in the worst possible position: growth is slowing and inflation is rising. Cutting rates would fuel inflation. Raising rates would crush growth. The OECD's report implicitly acknowledges there is no good monetary policy response to a supply shock of this magnitude — only a range of bad options.

The European Central Bank has already signalled it will hold rates at its next meeting. The Bank of Japan is stuck at near-zero. The Federal Reserve has made clear it will not cut until it sees inflation moving convincingly toward 2%. None of these positions are likely to change until the geopolitical picture clarifies.

The Bottom Line

The OECD report is not a forecast of disaster. It is a forecast of pain. Growth is slowing but not collapsing. Inflation is rising but not spiralling. The global economy is absorbing a major shock and bending rather than breaking — for now. But the margin of safety is thin, and every week the Hormuz blockade continues, it gets thinner.