The BIST All-100 Index (XTUMY) ended Friday, September 18, 2026, down 4.71% at 63,367.35 points. After closing at 66,502.43 points in the previous session, the index lost 3,135.08 points. XTUMY reached 64,202.42 points at its session high before falling to an intraday low of 62,840.86.