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 (Some coins with low trading volume may have their refreshes extended to 60s.), 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.