How do stock prices actually change?

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I understand how supply and demand works but I’m confused as to who actually is in charge of setting the price to display to all trading platforms. Since the stock price is constant across all trading platforms, what algorithm or system is in place to ensure there are no clashes or discrepancies between said platforms? Is there one dominating platform that monitors all stock prices which other platforms refer to such as the NYSE?

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Anonymous 0 Comments

There is no single mechanism to ensure the same price is shown for the same stock across different exchanges. If they are different, arbitrage traders will exploit this discrepancy such that the stock prices will become the same.

Depending on what platform you use, it can show you the prices on different exchanges (Bloomberg for example will do this where there are more than one trading venue).

Now if the prices differ between exchanges/venues, this will be exploited. If you can buy a stock for 99c and sell it on another exchange for $1 the prices are momentarily different until more people try and do that and the price is “arbitraged away”.

This is the case for dual listed stocks, e.g. some that are listed across different European exchanges and US at the same time.

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