MediumIV Macro Policy & Sovereign Debt15 September 2026, Tuesday · 18:10 TRT (UTC+3)
BIST 100 index falls 2.41% as the banking index drops 4.15%
Oil prices, bond sales and caution ahead of the Fed decision triggered a sharp sell-off on Borsa Istanbul.
The BIST 100 index closed at 13,892.30 points on 15 September, down 343.53 points or 2.41%, on trading volume of 177.4 billion lira. The banking index lost 4.15%, the holding index 2.29% and the technology index 4.62%. The index had stood at around 14,236 points the previous day.
The decline was driven by the rise in oil prices stemming from the Middle East, domestic bond sales and caution ahead of the US Federal Reserve decision. The 10-year benchmark yield rose to 32.83% on 16 September. Foreign investors had made net sales of 647.6 million dollars in equities in the week of 4 September; data for the week of 11 September will be released on 17 September.
Talay assessment
Bottom line
The 2.41% fall in the BIST 100 and 4.15% drop in banking show the external shock being transmitted to Türkiye simultaneously through oil prices, rising domestic yields and foreign outflows. The 10-year benchmark yield rising to 32.83% indicates the pressure is not confined to equities. While oil stays high and dollar rates tight, the most likely path is volatile trading under pressure, led by rate-sensitive sectors.
Likely effects
- Turkish banking sectorNegativeWeeks
Rising domestic yields create valuation losses in banks' securities portfolios and higher funding costs, which is why bank shares react more sharply than the index to oil and rate shocks.
- Türkiye public borrowingNegative1–6 months
A higher 10-year benchmark yield raises the Treasury's domestic borrowing costs and pushes up lending rates passed on to the corporate sector, potentially limiting growth.
- Foreign portfolio flowsNegativeWeeks
Net foreign selling of 647.6 million dollars in the week of 4 September shows the risk of continued outflows while global risk appetite is weak, weighing on lira assets.
Possibilities, ranked
- 1Volatile trading under pressure45%
Oil stays high and yields remain volatile; the market swings with sharp daily moves and banks drive volatility.
Watch: Foreign transaction data due on 17 September and the direction of the 10-year benchmark yield
- 2Deepening selling pressure30%
Oil and domestic yields keep rising and foreign outflows accelerate; losses widen, led by banks.
Watch: Net foreign selling in consecutive weeks and the 10-year yield holding above 32.83%
- 3Recovery25%
Oil prices fall and foreign inflows resume; yields decline and rate-sensitive sectors recover.
Watch: A sustained fall in Brent and net foreign buying in weekly data
Probabilities are calibrated judgement based on the sources, not measurement, and are revised as new information arrives. Not investment advice.
Market reaction
Indicators affected
- TR 10Y▲ 32.83%
Historical context