https://www.cmegroup.com/education/featured-reports/videos/the-equities-copper-ratio
Equities and copper tend to track each other, often one outperforming the other.
copper ratioequities
https://www.idcfp.com/blog/2021-04-29/copper-to-gold-ratio-forecast-a-2-4-yield-on-the-u-s-10-year-t-note-by-the-fall-of-2021-and-3-in-2022
coppergoldratioforecastyield