The ‘Octobull’ Myth Crumbles This Year: No Cause for Celebration
Jakarta, CNBC Indonesia — The so-called Octobull, associated with a rising stock market, does not appear to apply this year. The Jakarta Composite Index (JCI) has plunged by nearly 15% during October 2026, breaking the positive trend that has often prevailed in the month.
Over the past ten years, October has frequently been a positive month for the JCI. From 2016 to 2025, the index rose in eight out of ten Octobers.
The JCI’s strength in October gave rise to the myth of the ‘Octobull’, referring to the index being in a bull, or optimistic, market.
This October, however, has told a different story. Although the index closed higher today, by Wednesday (28 October 2026) it had already plunged 13% for the month. The decline is the steepest October fall since 2008.
A Month That Is Usually in the Green Turns Red
From 2016 to 2025, the JCI’s average October return was 1.16%. Its largest gain came in October 2020, at 5.30%, followed by October 2021, at 4.84%.
By contrast, only October 2018 and October 2023 ended in negative territory, falling by 2.42% and 2.70%, respectively. In the past two years, the JCI also recorded gains: 0.61% in October 2024 and 1.28% in October 2025.
This October’s JCI correction is far sharper than in previous years. Its 14.69% decline as of 28 October is the steepest for the month since 2008, when the index plunged 31.42% amid the global financial crisis.
Compared with all trading months over the past decade, October 2026 has also recorded the second-steepest decline. It is surpassed only by March 2020, when the JCI fell 16.76% amid the Covid-19 pandemic.
March 2026 ranks third, with a 14.42% decline. This means that two of the JCI’s three largest monthly falls in the past decade have occurred this year.
JCI Plunge Peaked in Mid-October
The sharp correction in the JCI this month was driven in part by a steep fall in the middle of the month. On Friday (16 October 2026), the index plunged 11.57% in a single day, its steepest daily decline since 1998.
The fall came after Morgan Stanley Capital International (MSCI) announced on 15 October 2026 that it was consulting on the possible downgrade of Indonesia’s market status from emerging market to standalone market.
The plan stoked investor concerns that Indonesian shares could be removed from global indices used as benchmarks by a number of fund managers. Selling pressure intensified, and trading was temporarily halted.
The JCI’s sharp correction also cut the Indonesia Stock Exchange’s (IDX) market capitalisation. As of Tuesday (27 October 2026), the IDX’s market capitalisation had fallen by Rp1,447 trillion, or 13.53%, from Rp10,695 trillion at the end of September to Rp9,248 trillion.
Selling pressure was also evident in foreign investor transactions. From 1 to 27 October 2026, foreign investors recorded net sales of Rp16.33 trillion. The largest sale came on 16 October, when net selling reached Rp3.34 trillion in a single day.
With the decline reaching 13% as of today, the JCI is on course for its worst October performance since 2008. The figure could still change, however, as trading for the month has not yet ended.