I remember reading this headline and then going and looking at the XMAG index[0].

YTD: +15.5%

1 year: +9%

Since inception (Oct 2024): +14%

Comparing that with S&P500

YTD: +16.7%

1 year: +13%

Since XMAG inception: +18%

The article should start with such a comparison but it just seems like a lot of text with very little numerical comparison, which makes it not very useful to conclude what the case is.

0: https://www.defianceetfs.com/xmag/

The MSN link on the post doesn't have the charts the original WaPo article [0] contains, which provide just such a comparison, though over a longer period (from 2019), showing 132% vs 1057%. (No idea if that is right or more/less meaningful, just pointing out it's missed off this link.)

[0] https://www.washingtonpost.com/business/2025/11/24/sp500-sto...

Correct! Backtest and compare ratios to common indexes!

If we made a similar comparison to the SP500 index since its inception in 1926, and made a chart of total returns difference over 1 year sliding window, between index and index minus it's top 7 performing stocks, i bet we will see this recent period isn't at all exceptional. Every economic boom is propelled by one or two sectors that have a limited number of players.