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).
“I haven’t encountered many who would try to put up more barriers for new users,” said Maria Shen, a partner at Electric Capital, a venture capital firm focused on cryptocurrencies. Still, she added, “the wallet space is fairly competitive, so it’s not unthinkable.”

Cryptocurrency prices continued to tumble Friday with Bitcoin leading the charge, with prices for the internet currency dipping below $50,000 for the first time since early March.
Yet some crypto watchers have raised red flags over SafeMoon’s unusual structure. It charges a 10% fee to buy tokens and another 10% to sell -- almost unheard of in the digital currency world. Half of these fees are paid to owners as an incentive to keep holding and the other half goes into a liquidity pool controlled by the developers. SafeMoon calls itself a DeFi token, or one that uses decentralized finance to govern functions through software, but it has a chief executive officer and chief operating officer. Critics also worry about the discretionary nature of the “manual” coin burns used to adjust its circulation.