Thursday, July 30, 2009

Computer trading makes markets better

The hype against high frequency trading is misplaced:
...some algorithms basically infer the price increase from trades, getting rid of the profits otherwise available. But these are all short term scenarios, and basically make a market efficient. That is, say Apple announces good news, suggesting a sharpe bounce in the stock. An investor tries to buy, and would like to trade 1MM shares, but clearly that's too much, so he puts in an order for 1000, then next minute, another 1000, and another. A machine might sense the pattern and basically jump on for the ride with him, diluting his profits. Is that bad news? Only for the short-term trader. For the longer run investor oblivious to this, who was on the other side, they got to sell at a higher price (the price rose faster than otherwise). The short-term speculator basically makes less because the algorithm reverse engineers his insight. This is the essence of an informationally efficient market, where news gets into the price asap. That those at the bleeding edge are making a profit is not a bug, it's a feature.

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