The AMX is one of the key stock market indices of the Amsterdam Stock Exchange in the Netherlands. Although not the leading index (that distinction belongs to the AEX), the AMX represents mid-sized companies in terms of market capitalization, ranking just behind the AEX in importance.

This index reflects the performance of the average Dutch market, and like other similar indexes, it is weighted by market capitalization. This means that companies with a larger market capitalization have a greater impact on the value of the index.

Many of the companies that are part of the AMX distribute dividends, and several of them are leaders in their respective sectors, although not as well known internationally as those in the AEX.

How is the AMX value calculated?

To determine the daily value of the AMX stock index, a mathematical formula based on the capitalization of its component companies is used:

AMX(t) = AMX(t - 1) × Σ Capi(t) / [ Σ Capi(t - 1) ± J ]

As with other indexes, a J-adjustment coefficient is used to ensure that financial operations such as capital increases or reductions do not drastically affect the share price.

The value of the AMX on day t is obtained by multiplying the value of the AMX on the previous day (day t-1) by a percentage calculated from the sum of the capitalizations of the companies on day t, divided by the sum of the capitalizations on day t-1.

The daily capitalization of a specific company is determined by multiplying the number of shares by their trading value on that specific day.

For example, if today the AMX closed at 500 points and the total capitalization of its companies is 200 billion euros, and tomorrow that capitalization would amount to 202.5 billion, the final value of the AMX for that day would be:

AMX (specific day) = 500 x 202.5/200 = 506.25 basis points.