To be honest, I don’t get the question. You know Citadel has probably 50% flow, how does knowing the rest of the 50% help? Watching outrageous option activity would help you a lot more.
The quick way to get the question would be to scan the past few pages of posts. Article: "How to Pick Stocks for Swing Trading" - https://finance.zacks.com/pick-stocks-swing-trading-11289.html In the article, "Adequate Number of Market Makers" is listed as a factor in the choice of stocks to invest in. So the natural question: Where is this information found? Who knew that determining the number MM's for major stocks would be so emotional and elusive?
%% PARTLY , same edge as any service business has. Partly, same edge as a service business like guns + ammo dealer has. Any hunter would know part of any seasonal patterns but not like a guns + ammo dealer. Olin [chemical ] Corp used to be part of Winchester Repeating Arms; +took me about 10+ years to find out[personal experience] they owned NILO Barge Lines . They since sold it , but just goes to show you how moving many tons + complex it can get, over the years.