They are the Market Makers, they create and assign all the fills, both public and institutional trades. The market makers ARE HUGE INSTITUTIONS, (ARCA, CDEL, etc) - - -they have ALL the power. All public orders have to pass through market makers hands. Every transaction on the entire exchange is underwritten by market makers. There is no public to public trading, the MMs broker all fills and get a fee for doing it (SEC transaction fee). MMs are "middle men" on every single trade, bar none. To make sure their lateral trade goes through uninterrupted, they simply sequence it to occur in that order in the fill sequence. It happens in tenths of a second, no one notices.
It's still all part of the same overall system, the shares still go through a MM, it's just that a private firm is then an additional layer brokering the trade for it's client. The ECN's get their shares from MMs. MMs have to underwrite any listed stock. No stock on the NYSE or NASDAQ, and even most OTC's, cannot get listed and trade on exchanges unless sponsored (underwritten) by a MM. Smaller listings may only have one or two MMs underwriting, while larger cap companies will have four or more.
So I have been led astray by the industry when I read " ECNs are the bane of market makers and empower individual traders with market maker-like features like placing hidden and iceberg orders." I understand that there is no market maker at an ECN. It's an electronic network that matches traders orders. Although there may be a requirement to have a MM to get a stock listed, the MM has no control over the ECNs. I could be wrong about that but that seems to be common wisdom.
I'm not sure why you're so interested in ECNs. What is your trading strategy and why would you want to pay an extra fee to a broker for orders you can trade for free on Robinhood, TD Ameritrade, Etrade, Fidelity, etc? What is your trading strategy, day trade, swing trade, or long hold? Since you won't get better prices or faster fills, what advantage do you think you have through an ECN? What kind of trading do you want to do? What are your goals?
I'm not interested in ECN's. I trade out of Canada and don't use Direct to market broker. My fills for the most part are good enough for me. I mentioned ECN's because you stated that MM's controled everything.
ECNs get their shares from MMs. What kind of trading are you doing and what are your goals? Big money controls everything, MMs are part of that system.
I swing trades stocks. My goals are to protect my capital while making superior returns so that I can fund my lifestyle.
What types of stocks do you trade (NYSE, NASDAQ,OTC), what price range, and what duration is your typical swing flip time, i/e trades/week?
TSE; NYSE; NASDAQ; $5 to whatever. I can buy a single stock if it's to price. Nope don't own any BRK I buy trending stocks and sell when the trend changes. I've sold the next day and held a stock for 9 years.