How do hedge fund managers know who is doing the buying?

I always hear big financial guys (RAY DALIO) say "we know who is buying and who is selling". Where do they get that info? He also said he pay 100's of millions for research, is that where the money is going? paying some company to find out who the buyers are? are the brokers giving clues? I've heard kramer claim the same thing. Are little guys not privy to this info?

 

Because after Gekko got done buying his broker (Bud) called the wall street journal and said 'blue horseshoe loves Anacott Steel' and then everyone on the street knew

 

seriously though, If you watch ray dalio's interview on cnbc he states "well I know who's buying but i dont want to give away a trade secret here". he's also like "we spend hundreds of millions of research" so how much does it cost to find out what the big buyers are doing?

 

Check 13F filings.

 

It's a very small world. Everyone knows each other. Kinda fraternity like is my description.

 

Relationships with brokers?

 

With each other. They tell each other what they are doing after work, on the phone, etc. I know a few of these guys and most of them are friendly with each other.

 

Paying someone that is willing to take the risk/fall.