Algorithmic Trading is Not High Frequency Trading

Algo trading has been around longer than HFT. It was invented to protect the information that that a big order was being executed. This avoided the risk of front running by handing the order to humans or scaring liquidity providers by executing it all at once.

HFT came about when computerized exchanges began to compete with each other for business. Nowadays you go hunting for liquidity. Speed differentials are more important.

I think the OP is likely to agree up until here.

Today HFT in its worst form amounts to high speed computerized rumor mongering. You game the market by bluffing orders and trading faster than your customers. The regulators will never catch on and try to fix it even thought the remedies are many and simple. Moreover our attitudes about who owns information make it very difficult for us to even consider these simple solutions.

HFT is a subset of algorithmic trading. It's as simple as that. Not all algorithmic trading is HFT. But all HFT is algorithmic trading.

Algorithmic trading is any type of trading done based on an algorithm, and not based on "traditional investing principles". For example, "buy when the 10-day moving average crosses over the 20-day MA, and sell when the 10-day it crosses below 20-day". One of the most famous types of this is Richard Dennis and the Turtle Traders, where a successful commodities trader took a bunch of ordinary people and tried to turn them into traders using this method.

I'm also an algorithmic trader. Not a wildly successful algorithmic trader yet, but I'm still learning and growing, and I love it more than any programming venture I've ever been involved with. And I haven't taken a catastrophic loss yet, so that's good. I trade on 3 separate markets using different algorithms, and for the most part it is fully automated. I'll hold futures contracts anywhere from 1 seconds to 20 mins.

HFT is several orders of magnitude more intense. For the most part, they are types of arbitrage, where they can arbitrage a few cents worth of difference in stock prices between different markets, and make a few pennies per 1000 shares. Or they will arbitrage between the price of an ETF or futures contract and the underlying basket of stocks that it represents. These are the ones that need colocation and trade on the millisecond. The more nefarious ones are the ones that game the system, by "quote stuffing", by frontrunning large orders by institutions, or by creating volatility through momentum-trading.

Is there a downside to algorithmic trading? Sure. Algorithmic trading is what has turned the stock market from a predictive market of future earnings, into essentially a casino, where the predictive nature of the markets is completely dead. Instead, it's about thousands of computers running random number generators and picking up nickels every 10 ms. This is why I believe there will be market crashes every 7-10 years, and long term investing is dead.

But unfortunately, this is the reality of the system that we live in, and we have to adapt or die. Or you can just buy bonds and get a stable 3-5% return every year, which is nothing to shake a stick at.