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[return to "Ask HN: What scientific phenomenon do you wish someone would explain better?"]
1. robert+XO[view] [source] 2020-04-27 02:51:18
>>qqqqqu+(OP)
If I buy a stock, does the price at which I agreed to buy it become the new share price on the stock exchange?

Every article on "Where do stock prices come from?" seems to just talk at a high level about supply and demand.

But where does the price come from at a nitty-gritty level? Is it an average of all existing offers or something?

Do different exchanges and stock-ticker websites have different formula for calculating share price?

If a very low-volume stock is listed at $4, and then I offer to buy a share for $100, does the NYSE suddenly start listing its price at $100?

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2. alasan+BQ[view] [source] 2020-04-27 03:11:35
>>robert+XO
If you see a single share price listed, that is the price of the last sale that occurred.

Now that can either mean that someone bought a share that someone else was selling or that someone was selling a share to someone who was offering to buy.

The shares are listed as a series of buy and sell orders in what's called an order book.

If the price a share was sold at was 100$ and you think it will go a bit lower, you could place a buy order at 90$. Should enough people sell shares to reach your price and order, your order will be filled and you will own the share at 90$.

If someone wants a million shares at 91$, you may not get your single share at 90$.

To go back to your example, if you were to place a buy order at 100$ for a 4$ priced share, how much the price moves depends on how many sell orders are in place from 4$ to 100$ and how much you are buying.

If it's only one for share, your order will probably get filled at something like 4.01$ if the spread is low (the spread being the difference between the highest buy order and the lowest sell order).

If you're buying 1000 shares and it's a low volume stock with a "thin" order book, maybe it could go up a few dollars instead but for it to go up to 100$ you have to buy every single share between 4$ and 100$.

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3. grecy+vZ[view] [source] 2020-04-27 05:19:34
>>alasan+BQ
How does it work with futures?

My understanding is that I buy a contract for 100 shares at a future date of my choice.

So let's say stock XYZ is currently trading at $20, and I buy a futures contract for $100 for Jan 1st 2021.

I don't have enough money sitting around to buy those 100 shares, so let's say XYZ is trading at $200 by Jan 1st 2021, That means I have a contract where I can buy 100 of them at $100 and immediately sell them for $200, so in theory it's a $10k profit.... but because I don't have enough money to actually do that, do I just sell my future for something close to 100* $200 (because someone with enough money will buy it and do the actual trade?)

What happens if it's already well over $100 long before Jan 1? Can I just set a price and sell it whenever I want like a can with a regular share?

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