The energy company Siemens Energy, which was only relegated from the Dax to the MDax in March, is returning to the leading German index this Monday (September 19). The recipe box supplier Hellofresh, which will be included in the index of medium-sized stocks with immediate effect, has to be eliminated.

The stock market value is the main factor determining the rise and fall of companies in the German stock market barometer. The index provider measures this based on the proportion of freely tradable shares in the individual companies. The volume-weighted average price in the last 20 trading days before the indices are checked is taken into account. As expected, it was no longer enough for Hellofresh to remain in the Dax. Since the beginning of the year, two-thirds have lost value. After a brief phase of stabilization, the share's downward trend picked up speed again in mid-August.

Index changes are particularly important for funds that replicate indices in real terms (physically replicating ETFs). There must then be shifted and reweighted accordingly, which can have an impact on share prices.