Wash cycle trading.

[readingstockport]

The HFT( High Frequency Trading ) Algorithmic Bots are faster than that - much , much faster . They can interparate newly released data & trade accordigly in speeds of 1 / 600,000 sec . They also front-run orders , which Exchanges in a desperate grab for marketshare are obligingly turning a blind eye .
I've traded Stock Index Derivatives & Interest Rate Futures for over 25 years now , holding positions over a very short timeframe of generally between 5 secs & 2 mins . Can't compete with these machines now , so now have switched to trading other markets - currencies & commodities , overwhat for me is a much longer period - typically between 6 hours & 3 days .

Yep, I said the average. When you have people holding equities for long periods then others doing high speed trading that is what has dragged the average down to 8 seconds or so.

and would 0.1% be an accecptable as a margin ?

If you are trading on millions of pounds or dollars hundreds of times a second then in the eyes of some comapnies and parasites then yes, very definately.

 

[Grendel]

it explains a lot about how share prices fluctuate up and down daily when in reality they should remain on an even upward slope (in most cases).

That's just plain wrong. Share prices are essentially a reflection of supply and demand, if no-one wants to buy shares in a company the price isn't going to increase. For a price to continually increase assumes that there's constant demand for a company's shares, and not so many people wanting to sell that the market has more sellers than buyers. If more people want to sell than buy, the price will decrease.