Introduction
The AEX Index is the benchmark equity index of Euronext Amsterdam, tracking the 25 largest and most liquid companies listed on the Amsterdam stock exchange. AEX stands for Amsterdam Exchange Index. It is the Netherlands' primary equity market indicator — the equivalent of the DAX for Germany or the CAC 40 for France — and is one of the oldest continuously published stock indices in the world, launched in January 1983.
For investors tracking European equities, the AEX is notable for two reasons: it is heavily concentrated in a small number of globally significant companies, and it is far more technology and semiconductor-weighted than most other European indices, making it sensitive to global tech sentiment in a way the DAX or IBEX 35 are not.
What the AEX Contains
The AEX consists of exactly 25 companies, reviewed and rebalanced annually each March. Composition is based on free-float market capitalisation — the market value of shares actually available for public trading, excluding shares held by strategic holders.
The index is capped: no single company can exceed 15% of the total index weight at rebalancing. In practice, that cap exists because of one company. ASML — the Dutch maker of the lithography machines that the world's chipmakers cannot do without — has grown large enough to hit the ceiling repeatedly, and on any given day it is usually the dominant force behind the index's direction.
Beyond ASML, the index reflects the particular shape of the Dutch economy rather than continental Europe broadly. Shell, the Anglo-Dutch oil major, gives the AEX significant exposure to Brent crude. RELX and Unilever — both dual-listed in Amsterdam and London — bring large, internationally diversified revenue streams that tether the index to sterling and dollar movements as much as to the euro. ING and ABN AMRO represent the Dutch banking sector, directly tied to ECB rate policy through their net interest margins. Adyen sits at the opposite end of the risk spectrum: a high-growth payments platform whose valuation swings sharply with sentiment toward European fintech. Heineken and NN Group round out the index with consumer goods and insurance exposure respectively.
How the AEX Is Calculated
The AEX is a free-float market capitalisation weighted index, calculated in real time during trading hours (9:00 AM – 5:30 PM CET) on Euronext Amsterdam. Dividends are not reinvested in the price return index — the AEX as typically quoted is a price index, not a total return index. A separate AEX Total Return index exists but is less commonly cited.
The base value was set at 100 on 3 January 1983. The index crossed 1,000 for the first time in 2021 during the post-COVID recovery and technology rally.
What Drives the AEX
ASML dominates. Because ASML regularly represents 15%+ of the index weight, its earnings reports, order intake data, and any semiconductor cycle news have an outsized effect on the AEX relative to other European indices. A 3% move in ASML on earnings day can drive a 0.5% index move on its own.
EUR/USD rate. Most large AEX companies generate significant international revenue in US dollars (Shell's oil revenue, ASML's chip machine sales, RELX's global subscriptions). A stronger euro reduces the euro-translated value of this revenue, creating a headwind for index earnings. The AEX is therefore more sensitive to EUR/USD moves than a domestically-focused index.
ECB monetary policy. ING and ABN AMRO are directly affected by ECB rate decisions through net interest margin expansion or compression. Rate-sensitive financials collectively represent a meaningful weight in the index.
Global semiconductor cycle. ASML's order book reflects demand from TSMC, Samsung, and Intel — the world's leading chipmakers. Any shift in the semiconductor capex cycle (driven by AI demand, smartphone unit volumes, or inventory correction) flows directly into AEX performance.
Historical Episodes
The AEX peaked during the dot-com bubble at 701.6 in September 2000, then fell 75% over the following three years — one of the sharpest declines of any major European index. The technology and telecoms exposure that drove the bubble was concentrated in the index. Recovery to pre-crash levels did not occur until 2021.
During the 2008 financial crisis, the AEX fell approximately 55% peak-to-trough, with ING requiring a Dutch government bailout. The experience restructured the Dutch banking sector significantly and led to ING's eventual strategic simplification.
In 2021–2022, ASML's rise to become Europe's most valuable company by market capitalisation transformed the AEX from a diversified European blue-chip index into one with significant semiconductor concentration — reshaping how global investors use the index to express views on the chip cycle.
What to Watch
- ASML quarterly earnings (January, April, July, October) — the single most important event for AEX direction; new order intake guidance moves the index
- TSMC monthly revenue data — proxy for ASML demand; strong TSMC revenue supports ASML order expectations
- EUR/USD rate — the AEX's embedded currency sensitivity; a weaker euro supports index earnings translation
- ECB rate decisions — directly affect ING and ABN AMRO; indirectly affect Adyen through fintech valuations
- Brent crude price — Shell's weight means energy price moves translate into index moves
- Semiconductor cycle indicators — SEMI equipment billings, DRAM contract prices, NVIDIA capex guidance — all influence ASML sentiment
- Annual AEX rebalancing (March) — changes in composition or cap-weight adjustments can cause mechanical flows into and out of constituents