ZSE sector indices: why CROBEXkonstrukt drops 4.85 % in a week when CROBEX stands still
The week of 4 to 11 September 2026 is a good illustration of something that keeps recurring on the Zagreb Stock Exchange: the headline index barely moved, while two sector indices lost almost 5 %.
CROBEX fell 0.17 % that week. CROBEXkonstrukt fell 4.85 %, CROBEXtransport 4.75 %. Over the same five sessions, CROBEXprime rose 0.84 %.
Weekly index changes on the ZSE
Official closing values for Friday 4 September and Friday 11 September 2026.
| Index | 4 Sep 2026 | 11 Sep 2026 | Weekly change |
|---|---|---|---|
| CROBEX | 4,390.81 | 4,383.13 | −0.17 % |
| CROBEX10 | 2,856.66 | 2,867.88 | +0.39 % |
| CROBEXprime | 2,302.68 | 2,321.91 | +0.84 % |
| CROBEXplus | 2,862.56 | 2,816.42 | −1.61 % |
| CROBEXindustrija | 3,864.70 | 3,855.41 | −0.24 % |
| CROBEXkonstrukt | 1,463.20 | 1,392.25 | −4.85 % |
| CROBEXnutris | 831.32 | 826.90 | −0.53 % |
| CROBEXtransport | 1,612.52 | 1,535.87 | −4.75 % |
| CROBEXturist | 6,025.51 | 5,898.02 | −2.12 % |
| ADRIAprime | 3,794.45 | 3,785.60 | −0.23 % |
| CROBIS | 98.0240 | 98.0240 | 0.00 % |
The spread between the best and the worst index in the same week is 5.69 percentage points — same exchange, same five trading days.
Why the spread is that wide
The answer is not that construction went through some drama the rest of the market missed. The answer is index construction.
CROBEX is a broad index. When one of its constituents drops 5 %, that move is diluted across dozens of other names, most of which moved little or not at all that day.
Sector indices — CROBEXkonstrukt, CROBEXtransport, CROBEXturist, CROBEXindustrija, CROBEXnutris — hold only stocks from a single sector by definition. That means three things at once:
- Fewer constituents. Each individual stock carries a larger weight, so its move is not diluted.
- Lower liquidity. ZSE sector indices include names that trade rarely, with a handful of transactions per day. For such stocks, a single trade can move the closing price by several percent.
- Correlated names. Stocks in the same sector often react to the same news, so moves add up instead of cancelling out.
The combination of these three properties means a sector index has a larger amplitude by its nature — not because more is happening in that sector, but because the sample is smaller and thinner.
The same pattern shows up day to day
These two days are from the same week:
- Thursday, 10 September: CROBEX −0.47 %, while CROBEXtransport was −4.28 % and CROBEXkonstrukt −3.73 %.
- Friday, 11 September: CROBEX +0.27 %, while CROBEXtransport was +1.38 % and CROBEXindustrija +1.23 %.
In both directions, sector indices move several times harder than the headline index. This is one phenomenon, not two separate events.
What this means for reading market news
When a headline says "the market fell", it almost always means CROBEX. That sentence is accurate, but it is also an average that hides a spread of nearly six percentage points.
A few practical notes when reading sector indices:
- Check the number of trades. A percentage change on a stock with one or two transactions is not the same information as a change on a stock with fifty. That figure sits next to the price in our screener and in the daily reviews.
- Watch for block trades. They can inflate daily turnover without moving the price — we covered this separately.
- A weekly move of 4–5 % in a sector index is not unusual in itself. For CROBEX the same move would be a major event; for CROBEXkonstrukt it falls within the normal range.
All official index values, updated after the close, are available on the Zagreb Stock Exchange indices page.
Data source: official closing values of Zagreb Stock Exchange indices for 4 and 11 September 2026. This text is informational and describes the movement of published index values. It contains no recommendation to buy or sell any financial instrument, and no forecast of future movements.