To quantify this, pre- and post- inclusion to the Global X...

To quantify this, pre- and post- inclusion to the Global X Copper Miners ETF on 01/05/24 (details here), the correlation between WA1 returns and copper futures returns has gone from 0.08 to 0.45 (I use rolling 3-day return in this estimator to reduce the effect of asynchronous hours), meaning copper is now a significant explanatory factor in WA1's returns. As discussed previously, there are real economic linkages between these metals for various reasons, but there is also now a mechanical effect, i.e. sell-off in copper => outflows from COPX => WA1 shares sold. For example, since the beginning of July, COPX's 1.6m share WA1 holding has reduced by ~100k shares due to outflows.

Correspondingly, the beta for WA1 returns against copper returns in the post-inclusion period is ~1.5, i.e. there is an expected 1.5% change in WA1 price for each 1% change in copper price. As the copper price has declined ~9% since peaking on May 20th, incidentally when WA1 peaked, the expected decline in WA1 price attributable to the copper move is ~14%.

Just something to think about..

P.S. Thanks @Naydoe, interesting!