The first problem is the confusion of causality. If the oversold of stocks in the programmed trading strategy led to the stock crash of 1987, what caused the start of these programmed trading in the first place? According to the waterfall effect assumed by the US Securities and Exchange Commission, the stock futures price must be lower than the share price by a certain percentage before the arbitrageur sells the stock and causes the stock market to crash. So what caused the initial discount of futures relative to stocks? Those fallacies that accuse programmed trading are all based on their vicious circle theory, which is based on the premise that futures prices have fallen sharply and become discounted, leading to contradictory causality. From another perspective, programmed trading is not an accidental self-sustaining process, but is triggered by some factors. These factors are exactly what we are looking for, but they are ignored by those who are accused of programmed trading. If the public only pays attention to one of the many reasons leading to the stock market crash, it is likely to ignore the main reason and simplify the cause of the stock market crash. The second problem is that programmed trading cannot affect two markets at the same time in the early days. According to the vicious circle theory, when an arbitrage trader notices that stock index futures are undervalued relative to the spot index, he will buy Chicago S&P index futures and sell all the constituent stocks of new york S&P index. Selling stocks will cause the new york stock market to fall, which will force portfolio insurance companies to sell Chicago futures hedges. Obviously, only when the new york and Chicago markets open at the same time, can programmatic trading have an impact on the two markets. However, before the new york stock market opened in June 1987+ 10/9, the Standard & Poor's index futures traded in Chicago had fallen by 7% in weekend trading, reaching the biggest one-day drop since June 1940. In other words, the first wave of futures declines occurred on the morning of June 10, June 17 and June 19, and were limited to the Chicago futures market. At this time, the arbitrage trader is spending the weekend, and before the programmed trader returns to the computer screen, the stock market crash has already occurred, so it is certain that the first stage of the market decline is influenced by other reasons rather than programmed trading. Richard Lohr criticized the authoritative organization's view that programmed trading was the first disaster in the stock market in the article 1987+00 June. Richard pointed out that a large number of programmed transactions in the American market are not the main reason for the stock market crash, otherwise the market may have plummeted long ago, and there must be a potential "trigger mechanism". Richard believes that the US trade deficit, the market's fear of economic recession and even the expectation of the 1988 election may be the reasons for the stock market crash, but no one can convincingly prove the real reason for the 10 decline. In order to better understand the stock market crash of 1987, Richard turned to study the international financial market before and during the stock market crash. He found that the stock markets in Asia, Australia, Europe and North America plunged around the world at the same time as the US stock market crashed. Moreover, at that time, programmed trading was not popular in the global financial market, and only the American financial market existed in large numbers. If programmed trading led to a 22% decline in the US market, why did other financial markets without programmed trading also plummet?