The total BTC amount of the top 10 transactions (in terms of total BTC sent) divided by the total BTC amount flowing into exchanges.
Find Whale Focused Exchanges with Top 10 Inflows. Looking at the relative size of the top 10 inflows to total inflows, it is possible to discover which exchanges whales use. For example, as Gemini has mostly whale users, it is possible for the price to rise or fall dramatically. This has potential risks, but also the possibility of arbitrage.