Phemex’s Index Price is derived from six spot exchanges: Coinbase, Bitstamp, Kraken, Binance, OKex, and Huobi. For instance, in terms of BTC/USD, we derive our trading price directly from Coinbase, Bitstamp, and Kraken. In terms of BTC/USDT, the price on Binance, OKex, and Huobi will first be converted into BTC/USD based on the USDT/USD price instead. If any of these exchanges fail to update their price for a 15s period, they will be temporarily removed from the calculation. The highest and lowest prices are also removed before calculating the average. A minimum of three qualified prices is necessary to update the Index Price, otherwise it will remain the same.