(Bloomberg) -- Equity investors are learning a harsh lesson this corporate earnings season: Not all artificial intelligence trades are created equal. And yet, the S&P 500 has gone nowhere since the season began in mid-July, weighed down by the largely underwhelming response to big tech. On the other hand, European stocks are seeing the boost from strong results as they have a lower concentration of tech heavyweights. "We had reduced our exposure to the US and rotated partially to Europe prior to the earnings season," said Amelie Derambure, a senior multi-asset portfolio manager at Amundi SA. "We weren't comfortable with the weight and concentration on the broad AI theme, but we were expecting Europe to deliver on demanding expectations in terms of earnings — and it did."