The SADF test finds the largest ADF statistic from all the windows considered. If this value exceeds a critical value, the null hypothesis can be rejected, and it is deemed the series displays explosive behaviour in at least one of the windows (taken as indication of a bubble occurring).
Vavilov said he had found an “immediate energy fit” with Brooks, who was acting chairman of the Office of the Comptroller of the Monetary Authority, a US banking regulator until January. He previously worked as Chief Legal Officer at the cryptocurrency exchange Coinbase.

But it wasn’t just outside pessimism that led to the slump, but infighting as well. Blockchains are decentralized, and democratic systems require buy-in from participants in order to keep the engines running. When there’s a schism that can’t be decided by the majority, all hell breaks loose.
In order to provide a methodology to detect bubbles in time series, Phillips, Wu, and Yu [23] proposed the supremum augmented Dickey-Fuller (SADF) test. This applies a series of right-tailed unit root tests to expanding windows of a time series (with a fixed start date), defined by where r2 is the final data point to be considered in each window, starting at r0 which is a fraction representing the smallest allowed window size and expanding to 1(the complete data set).