Sharp Decline in Borsa İstanbul Following Capital Markets Board Fund Regulation
Following the CMB's investment fund regulation, major value losses were seen in stocks on Borsa İstanbul, while the BIST 100 index closed the day lower after the circuit breaker system was triggered.
Following the Capital Markets Board's updated guide on investment funds, a significant portion of stocks on Borsa İstanbul lost value. As the selling pressure deepened, the circuit breaker system was triggered in the BIST 100 index.
Investment Funds Regulation and Market Impact
The investment fund regulation implemented by the Capital Markets Board on August 29 triggered a widespread downward wave on the stock exchange and put investors in a difficult position.
In Borsa İstanbul, where a total of 625 companies are traded, company shares associated with free funds or experiencing liquidity problems were subjected to heavy selling pressure.
Value Losses in Stocks
In the 18-day period following the fund regulation, 34 company stocks lost 33 percent or more, and 132 company stocks lost over 20 percent of their value.
While Hedef Holding and Pasifik Eurasia stocks experienced a 74 percent drop, these companies were followed by Odine Teknoloji and Gündoğdu Gıda.
Circuit Breaker and Market of the Day
The BIST 100 index on Borsa İstanbul activated the Index-Based Circuit Breaker System after losses exceeded 6 percent in the second half of the day, and trading was temporarily halted.
The BIST 100 index completed the day with a 5.54 percent decline at the 13,122 point level.
CMB Guide and New Ratios
The Capital Markets Board updated its investment funds guide with its decision dated August 28, 2026, in order to limit the concentration risk that free funds may create in stocks.
According to the new rules, the maximum ratios that free funds can purchase from free-float shares were redetermined between 2 percent and 8 percent, depending on public float rates.