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The World Cup is a genuine, enormous attention shock — Wikipedia traffic spikes eightfold during the final. Yet a new working paper finds the World Cup stock market effect barely registers in the deep, global markets that carry most of the world's money, and shows how two ordinary ways of measuring it can conjure the effect out of nothing. Where the distraction does bite is among retail investors trading on the noise — the people the original studies never quite looked at.

A new working paper has documented the largest price inefficiency ever found in the stock market: a pure-news signal with a Sharpe ratio of 3.1, more than double any known factor. But the researchers used a frontier AI model, millions of news articles and institutional trading costs to find it — and the same evidence that shows markets are inefficient also shows why an ordinary investor still can't beat them.

How often should you check your investment portfolio? Probably far less often than you do. The 56/44 daily split of up and down days in the stock market, combined with the human tendency to feel losses twice as keenly as gains, means daily checking is almost mathematically guaranteed to make you miserable. Ben Carlson's new book Risk & Reward sets out the evidence — and the practical moves that protect long-term investors from their own short-term instincts.