A stock's price moves up or down when a trade is executed with a price above/below the market price. I was wondering if there's more to it than that. For example, does a trade have to have a certain value/volume to be eligible for moving the price? Do different exchanges have different rules regarding this matter? I'm really interested to know what different exchanges are doing.
The market is an auction. Volume moves price
If the current price is $50.00 by $50.05 with a size of 40x50, it will take the purchase of 5,000 shares to take out all of the shares offered at the ask price of $50.05. Those 5,000 buy side shares could be 50 people buying 100 shares each or one person buying 5,000 shares. The number of buyers is irrelevant.
If no one else comes in to sell shares at $50.05 (new orders) then the ask price will become the next higher priced sell order on the order book. If it is $50.10 then the quote changes to $50.00 x $50.10.
If someone were to then come in with a buy order at $50.05 then the quote would become $50.05 x $50.10. As long as buying pressure keeps taking out the ask volume then price will continue to rise. When it buying pressure fades, price will cease rising and will remain static. When this process reverses, share price will drop.