The SPDR STI ETF (SGX: ES3), an exchange traded fund that mimics Singapore’s Straits Times Index (SGX: ^STI), returned 13.1% in the first half of 2026. A respectable showing. Yet all three of Singapore’s biggest banks left it behind. Oversea-Chinese Banking Corporation (SGX: O39), or OCBC, led with a total return of 28.2%. Over the same period, DBS Group (SGX: D05) returned 19.3% while United Overseas Bank (SGX: U13), or UOB, offered a 15% return. The trio make up the largest components of the 30 index constituents, and all three came out ahead of the benchmark. Here’s the twist: net interest margins (NIM) are falling during the period. In other words, margins are being compressed at every bank. If so, why did these three come out on top?

What powered OCBC to the front?

OCBC delivered a record total income of S$3.8 billion for 2026’s first quarter (1Q2026), up 5% year on year (YoY). Yet, over the same period, net interest income fell 5% to...