I have some preliminary research for you:

https://github.com/Rucknium/misc-research/blob/main/Monero-Black-Marble-Flood/pdf/monero-black-marble-flood.pdf

March 2024 Suspected Black Marble Flooding Against Monero: Privacy, User Experience, and Countermeasures

On March 4, 2024, aggregate Monero transaction volume suddenly almost tripled. This note analyzes the effect of the large number of transactions, assuming that the transaction volume is an attempted black marble flooding attack by an adversary. According to my estimates, mean effective ring size has decreased from 16 to 5.5 if the black marble flooding hypothesis is correct. At current transaction volumes, the suspected spam transactions probably cannot be used for large-scale “chain reaction” analysis to eliminate all ring members except for the real spend. Effects of increasing Monero's ring size above 16 are analyzed.