The mechanism behind this is straightforward once you see it. Nigerian Exchange Limited designs its indices using a market capitalisation methodology, and reviews constituents twice a year, at the opening of trading on the first business day of January and of July, with companies added or dropped and further adjustments possible around mergers, suspensions or resumptions. Under this design, a stock's pull on the index is its price multiplied by the number of shares in issue. A company worth N15 trillion moves the needle far more than one worth N50 billion, no matter how many investors actually trade either on a given day.
BusinessDay's March 2026 snapshot shows why that matters. At the time, MTN Nigeria was the single largest listed company at N15.9 trillion, contributing 12.3% of total market capitalisation. BUA Foods followed at N14.4 trillion and Dangote Cement at N13.7 trillion. On 16 March 2026, BUA Cement hit the N10 trillion mark after a maximum daily limit gain, rising to N11.1 trillion by 23 March and overtaking Airtel Africa, which then stood at N8.53 trillion. With BUA Cement in fourth place, BusinessDay put the top four firms at roughly N54 trillion between them. One stock's limit-up session was enough to reshuffle the ranking of the market's biggest names.
The trading data behind the headline number tells a separate story. On the day the ASI first crossed 200,000 points, closing at 201,156.86 with a year-to-date return of 29.27%, about 948.1 million shares worth N49.15 billion changed hands, concentrated in a handful of banking and blue-chip names, BusinessDay reports. The average daily value traded across 2025 was N23.76 billion, and in some sessions as many as 57 stocks recorded no price movement at all. A 29.27% rally and a market where over 50 stocks sit frozen for a session are not contradictory. They are the same market, described from two different angles.
This is not a one-off snapshot either. Nairametrics reports that nine megacap companies, those valued at N5 trillion or above, added N46.69 trillion in combined market value between December 2025 and August 2026, which was 79.9% of the N58.36 trillion increase in the entire NGX's market capitalisation over that period. Three names alone, Airtel Africa, Dangote Cement and MTN Nigeria, added N28.53 trillion between them, about 61% of the total gain across all nine megacaps. Airtel Africa's own market value rose from N8.53 trillion to N23.68 trillion, a 177.5% increase, making it the largest contributor to the entire group's growth. By the end of August, Airtel Africa was the largest of the nine megacaps, so the March ranking above had already been overturned. The concentration behind the ASI's rise is not stable; it is getting tighter.
There is a further layer to this that headline market-cap figures do not show. Nairametrics found that major shareholders in ten of the NGX's largest companies hold stakes worth an estimated N73.11 trillion, equal to 46.18% of the entire Exchange's market capitalisation. Dangote Industries holds 86.65% of Dangote Cement, a stake Nairametrics valued at about N15.12 trillion at 31 July prices. Abdul Samad Rabiu holds 92.64% of BUA Foods through direct and indirect interests. MTN International (Mauritius) owns 73.39% of MTN Nigeria, and Airtel Africa Mauritius holds 62.73% of Airtel Africa. As Nairametrics puts it, this means headline NGX market capitalisation does not necessarily represent the amount of equity readily available to public investors.
So read the ASI as a report on a handful of giants, not on the whole market. When it jumps, check which of the big names moved before deciding that Nigerian stocks broadly went up. A broad rally shows up as gains spread across many stocks and real trading value outside the banking and blue-chip names, not in the index figure alone.
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