Rarely does a tech-powered stock rally come along that isn’t pilloried for the fragility of its foundation. Now, with a snowballing craze for artificial intelligence pretty much propping up the market by itself, the haters are out in force. Never has so much been owed to so few when it comes to the recent upward arc of indexes like the S&P 500 and Nasdaq 100, upon which trillions of passively invested dollars ride. The top-heaviness of advance, on display all year, can be seen by comparing the Nasdaq 100 to a version of the same index that strips out its market-value biases. The equal-weighted one, which treats ... (full story)