Over the Counter (OTC) cryptocurrency trading is becoming increasingly popular across the globe. Her...: Over the Counter (OTC) cryptocurrency trading is becoming increasingly popular across the globe. Here’s how it works, who the major players are, and its general pros and cons. OTC market size In April 2018, Bloomberg reported that the daily OTC market was anywhere between $250 million and $30 billion per day. This is compared to around $15 billion per day on crypto exchanges. The volumes being reported vary wildly. Bravecoin.com reported in April that the daily OTC volumes were three times the size of exchanges2.