Among the most commonly raised risks are potential

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he speed of transactions and the daily volume of orders placed by THF software, while not a threat in the strict sense, have a real influence on global markets. This influence has already been felt in the past during stock market crashes and computer incidents that have had a phenomenal impact on the world's largest stock exchanges.

market manipulation, increased zalo database instability and flash crashes, but also the facilitation of insider trading and the eventual disappearance of “traditional” investors. Indeed, many analysts fear first of all that algorithms will be used on a large scale and in a coordinated manner to manipulate prices . This would allow HFT companies to drive down the price of a stock in order to buy it en masse before its price returns to normal. This type of manipulation could lead to very rapid crashes , followed by a longer period of instability, due to the distrust of third-party investors .

Less dramatically, the proximity of HFT companies to stock exchanges and trading platforms could allow a few high-frequency traders to have access to important information before everyone else. This would be on the verge of insider trading without really being one…, thereby creating inequality and a strong feeling of injustice among traditional investors . These investors could even disappear in the long term, because they can no longer rely on a fundamental analysis of the companies and stocks in which they invest their capital.

These fears have already proven true on a few occasions in recent years. In 2012, a bug in Knight Capital's HFT system caused it to lose nearly $440 million . The random and massive orders made the market so unstable that the company's stock quickly fell to less than $3 after erratic fluctuations occurred in the largest companies such as Novartis (-4%), Nokia (+9%) and Goodyear (+10%). The same type of situation caused a sharp fall in the Dow Jones in 2018, followed by the CAC40 , which dragged down the Asian and European stock markets with them. It is therefore easy to see that even if HFT only focuses on microtransactions, these are so numerous that their "mass" has a real impact on markets on a global scale.

However, high-frequency trading does not only have disadvantages on a large scale. It does indeed increase the liquidity and "depth" of markets by facilitating transactions and making them much more fluid. The speed of execution of orders thus obtained then helps to reduce the maximum price gap over short periods. We therefore obtain a share or an asset at a price that is much closer to its "fair" price, or to an average value calculated on a much larger number of orders.