Re: Algorithmic trading
Nobody picks the stocks.
HFT is mostly either arbitrage (this stock in London is 0.1% cheaper in New York if the exchange rate from GBP->Euro->USD is slightly less than X.)
Or front running; people are buying stock X so if I am 0.1km closer to the exchange I can buy it 100us before them and resell it for 0.1% more.
Or market watching; a big pension fund has to hold 30% of a certain class of bonds. On the last payday of the month it will get a huge chunk of new money which it has to buy these bonds with, so just before this the price goes up.
HFT can be a good thing in that it makes the market more efficient, everybody gets to buy Apple for the same price, anybody attempting to sell apple for 0.1c more is going to get zero business. That's why some IPOs and those little "only certain customers can buy these stocks" deals that a bunch of (now bankrupt) merchant banks did - are so bad.