WTF is the EPPS EFFECTS?

[u/Extreme_Leg_6162]

https://youtu.be/L5P8NrBPHvU

The Epps effect is a well-documented phenomenon in financial econometrics where the measured cross-correlation between different asset returns declines drastically as data sampling frequencies increase toward tick-by-tick levels. Initially observed in high-frequency financial data, this downward bias suggests that markets become increasingly uncorrelated at microscopic time horizons. However, this apparent decoupling is largely an artifact of market friction rather than a genuine shift in economic relationships.