Block trades on the Zagreb Stock Exchange: why daily turnover spikes without a price move
On 4 September 2026 the Zagreb Stock Exchange recorded roughly EUR 1.75 million in equity turnover. That sounds like a decent day. Break the number down, however, and the picture changes: a single transaction accounted for EUR 357,000, or about 20% of the entire day's turnover, and one stock — Atlantic Grupa (ATGR) — represented around 58% of everything traded that day.
This is not an anomaly or a data error. It is a normal feature of a small market, and it is exactly why daily turnover should not be read as a measure of how active the exchange was.
What actually happened on 4 September
In the Zagreb Stock Exchange official end-of-day file, ATGR appears that day in two separate rows:
| Trades | Shares | Turnover | Price | |
|---|---|---|---|---|
| Regular trading | 22 | 12,886 | EUR 655,420 | VWAP 50.86, close 51.00 |
| Separate entry | 1 | 7,000 | EUR 357,000 | 51.00 |
The second row is one transaction of 7,000 shares at a flat price of exactly EUR 51.00, with no percentage change reported. That is the pattern typical of pre-arranged (block) trades — deals in which two parties agree on size and price in advance and report them to the exchange for publication.
For comparison, regular trading in ATGR that day consisted of 22 transactions at a volume-weighted average price of EUR 50.86 — so genuine trading took place around similar levels, but in far smaller pieces.
Why this changes how the numbers read
Three practical consequences:
1. Turnover is not liquidity. Strip out that single pre-arranged deal and the EUR 1.75 million falls to about EUR 1.39 million. Strip out ATGR entirely and the rest of the market traded around EUR 735,000 that day, across the 38 remaining stocks with trades. That is a materially different day from the one the headline figure suggests.
2. Percentage change and turnover describe different things. A block trade at a flat price typically does not move the closing price. CROBEX ended 4 September at 4,390.81 points (+0.02%) and CROBEX10 at 2,856.66 (+0.17%) — a quiet day by price action, despite the "large" turnover.
3. Turnover rankings distort easily. A stock that tops the turnover table one day because of a single arranged deal often sits near the bottom the next. For judging liquidity it is more useful to look at the number of transactions over a longer period than at turnover on any one day.
How to check this yourself
When a daily list shows unusually high turnover, check three things:
- The trade count. Large turnover on one or two transactions almost certainly means an arranged deal. The screener lets you compare stocks on several parameters at once.
- VWAP versus the closing price. In a block trade they are frequently identical, because there is only one price.
- Whether the index moved. The ZSE indices show whether the market actually moved or the turnover was merely technical.
The reverse logic holds too: a day with modest turnover but a high number of transactions spread across many stocks is often a healthier picture of the market than a day carried by one large deal.
The Croatian market context
On a market the size of the Zagreb Stock Exchange this is a structural issue rather than an exception. The number of stocks traded on any given day runs in the dozens — on 4 September there were 39. When an institutional investor on such a market wants to move a large block, the regular order book struggles to absorb it without a significant price move, so the trade is arranged directly. The result is that one transaction occasionally dominates the entire daily statistic.
For anyone following the market the takeaway is simple: always decompose daily turnover before drawing a conclusion from it.
This article is informational and educational. It describes how publicly published turnover data is structured and how to read it; it contains no recommendation to buy or sell any financial instrument and no forecast of future prices. Data source: official Zagreb Stock Exchange end-of-day file for 4 September 2026.