arbitrage is difficult because the market is stupidly inefficient, but yes, the prices do more or less correlate. e.g., last night when they arrested the fall

arbitrage is difficult because the market is stupidly inefficient, but yes, the prices do more or less correlate. e.g., last night when they arrested the fall with 100m more Tethers, the price shot up $1000 on Bitfinex and about $400 on GDAX a bit later.