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Jukka Blomberg
Jukka Blomberg

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Wine stocks are up 6.5% since July. Or down 2.8%. It depends how you count.

#datascience #opendata #finance #data

Here is one small dataset with two honest answers.

Take the 22 listed wine companies in the BoomCellar Wine Stock Index (13 countries, 16 exchanges). Start them all at 100 on 3 July 2026 and read the close on 6 October 2026 (USD):

  • Weighted by company size (the index): 106.50, so +6.5%
  • Every company counted once (the equal-weight companion): 97.17, so −2.8%
  • World equities, for scale (iShares MSCI World ETF, URTH, rebased the same day): 103.49, so +3.5%

Same companies, same prices, same dates. The only thing that changes is how much each company counts.

Why the two lines split

Size weighting gives a big company a big say. In this index one company, Treasury Wine Estates (Australia), is about 43% of the weight today. The top three (with Yantai Changyu in China and Concha y Toro in Chile) are about 67%.

So the weighted line mostly tells you how a few large producers did. The equal-weight line tells you how the typical listed wine company did. Over these three months those two stories are different: the headline is up and beating world stocks, while the average company is down.

Neither number is wrong. They answer different questions, and a single headline number hides which question it answered.

How the comparison is built

  • The index is market-cap weighted; the equal-weight companion gives each company 1/N at the base date and, from now on, resets to 1/N at the last session of each calendar quarter (first reset 31 December 2026).
  • The world line is the market price of a listed ETF, rebased to 100 on the same day. It is a reference line, not a licensed index.
  • Levels before 3 July 2026 are back-calculated from today's companies, so they leave out firms that failed or delisted. That is why this note only uses the live period since the base date.
  • The full method is versioned and has a DOI: 10.5281/zenodo.23092835.

Get the data

Both series and the comparison are free to use with attribution:

  • Index page with the "Equal weight" and "World ETF" toggles: boomcellar.com/indices/wine
  • Downloads and data dictionary: boomcellar.com/data
  • JSON: https://boomcellar.com/api/series/wine?vs=world and https://boomcellar.com/api/series/wine-ew

If you want the monthly read of these numbers in your inbox, the Brief sign-up is on the index page.

Information, not investment advice.

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