# How do most arbitrage opportunities account for unknown volume at a ticker price?

So, from a conceptual level, arbitrage seems quite forward... buy at one place at one price, and sell somewhere at a higher price. However, after doing some initial digging it appears to be not quite as straightforward as initially appears.

Currently, I can't seem to get my head wrapped around how to handle tickers just quoting a price, without quoting a volume. Example below:

• Assume equal bid/ask price, for simplicity sake.

• Asset A, exchange 1 ticker: $100. • Asset A, exchange 2 ticker:$101.

• Each exchange has a \$10 transaction fee.

So, in the above example, at least 20 units of Asset A need to be purchased from exchange 1 and sold at exchange 2 to cover the cost of the transaction fees and take advantage of the arbitrage opportunity.

From my understanding, the volume availability isn't known until a limit/market order is placed on both exchanges, and even if it can be listed at ticker price time it doesn't seem like it would be safe to assume that all conditions will remain the same from the time that the ticker is examined to the time that an order is fulfilled. So in practice, how is this situation handled?

Just place a limit/market order and hope that there is sufficient volume? If there isn't sufficient volume, do the losses just get eaten?

For additional context, I am mainly interested in the trading of cryptocurrency.

• Are you familiar with Level II quotes? they show the prices and amounts available en.wikipedia.org/wiki/Financial_quote#Level_2_Access So you CAN see both quantities and prices. – Alex C Mar 14 '16 at 0:56
• Thanks, @AlexC, I was actually unaware of that. Even with this additional knowledge of volume, though, it doesn't be a certainty that the volume quoted at the ticker will actually be available at order fulfillment time? – Brent Hronik Mar 14 '16 at 1:46
• Yes, you are right. You have to be quick and lucky... – Alex C Mar 14 '16 at 8:49
• That's why it's called an opportunity ;) You can't eliminate this risk completely, but you can minimize it by being very fast. – Bob Jansen Mar 14 '16 at 9:46
• Ok, cool, I wasn't sure if there was anything more sophisticated that I was missing. Ideally something along the lines of locking in quoted price/volume on multiple exchanges simultaneously, and only executing the orders when it is certain that sufficient volume can be met? – Brent Hronik Mar 14 '16 at 16:34