The Financial Post reports in its Tuesday, March 12, edition that U.S. stocks' torrid climb to start 2024 is evoking worrisome comparisons with past boom-and-bust cycles. A Bloomberg dispatch to the Post reports that there is ample reason to wonder whether shares have climbed at an unsustainable pace. The S&P 500 index has closed at record highs 16 times this year, accounting for about a third of all trading days; Nvidia has soared nearly 80 per cent, adding about $1-trillion (U.S.) in market value, even after sliding on March 8 along with other tech shares. Yet there are signs that the strength, based in large part on the economy's resilience and robust corporate earnings, has not turned into a speculative frenzy. Several of the so-called Magnificent Seven stocks have sputtered, showing that investors are not throwing money at the market with abandon. The muted reaction to initial public offerings of late also supports that notion. What is more, an equal-weighted version of the S&P 500 just hit a historic high, indicating the rally is broadening out. Valuations of the benchmark's biggest stocks are well below levels seen for the market leaders at the height of previous market cycles.