Donald Trump has a tumultuous relationship with the Stock Exchange.

With his tweets, he often changed the financial markets which now bet on Joe Biden.

Nicolas Barré takes stock of a current economic issue.

Since the first day of his mandate, Donald Trump has multiplied the tweets at each Wall Street record.

Wall Street which, today, is betting more on its defeat.

If there is one subject on which Donald Trump has not changed tack, it is the Stock Exchange.

A simple line: when Wall Street goes up, it's thanks to it, when it goes down, it's the fault of others like China, the central bank or oil.

The point is that during his tenure the US stock market rose a little over 50%.

Nice performance then.

But the fact is, too, that she had progressed in the same proportions under her predecessor Barack Obama.

What is more annoying for the incumbent, however, is that Wall Street had its worst performance in October since the spring.

And never since 1932, the US markets had fallen so much the week before the election, with a drop of 5.6%.

Should this be seen as a bad omen?

It is not very good indeed.

55% of American households own stocks, so they are very sensitive to changes in the stock market and Trump has spent his time linking his fate to stock indexes.

At the beginning of September, when Wall Street crossed the 29,000 points, he could not help but take credit for it in one of his 55,000 tweets: "you are lucky to have me as president", writes -he.

Adding that with Joe Biden, "the market would collapse".

Bad luck, that's what happened in recent days.

Now the financial world, you know, loves statistics.

And in particular this one: when the S&P 500 index, the Wall Street barometer, falls during the three months preceding the election, the candidate president loses the White House.

This has happened every time since World War II except once, in 1956, with Dwight Eisenhower, a Republican.

The statistics are against Trump.

He is a president who has often tried to influence the stock market.

This is an atypical or even unique case in American history.

Barron's magazine, the Bible of American stock marketers, has reviewed its tweets and noticed that it is between 6 and 9 a.m., before the markets open, that it sends the most tweets.

With a direct influence on the Stock Exchange, for example when it announces tariffs on Chinese products, which immediately brings down Wall Street.

Worse, he tweeted about listed companies like Ford, Boeing, Exxon Mobil, Harley-Davidson etc.

to say good or bad: if the tweet is positive, the stock gains on average 1.4% on the same day.

If it is negative, it loses a little more than 1%.

It borders on price manipulation.

It's a misdemeanor, but Trump isn't close.