STOCK MARKETS, Wall Street-wary politicians and like-minded commentators repeat ad nauseam, are not the real economy.(股市，警惕华尔街的政客们和志同道合的评论员们不厌其烦地重复，并不是实体经济。) The S&P 500 index of America’s biggest firms is up by 12% this year, setting one all-time high(历史新高) after another. Meanwhile, they note, though American GDP growth has been steady and unemployment is fairly low, consumers feel more downbeat(悲观的，沮丧的) than at just about any time since the University of Michigan started keeping track in 1952.
股市，警惕华尔街的政客们和志同道合的评论员们不厌其烦地重复，并不是实体经济。美国最大公司的标普500指数今年上涨了12%，屡创新高。与此同时，他们指出，尽管美国GDP增长稳定，失业率也相当低，但消费者的情绪却比密歇根大学自1952年开始追踪以来的几乎任何时候都要悲观。
All true—and nauseatingly familiar. Less remarked is the fact that the S&P 500 and the world’s other benchmark(基准，基准指数) indices are no longer the real stock market, either. Rather than mirroring the universe of domestic equities, they increasingly reflect the fortunes of a few corporate giants, which in turn mostly rise and fall with the unstable outlook for the artificial-intelligence revolution. This is making many benchmarks—and, by extension(由此推及，进而), the stock portfolios and pension pots of investors everywhere—considerably more volatile(波动大的，不稳定的).
这一切都是真的——而且令人作呕地熟悉。较少被提及的事实是，标普500和世界其他基准指数也不再是真正的股票市场。它们不再反映国内股票的整体情况，而是越来越多地反映少数企业巨头的命运，而这些巨头又大多随着人工智能革命的不稳定前景而涨跌。这使得许多基准指数——进而推及世界各地投资者的股票投资组合和养老金账户——波动性大大增加。
Take the S&P 500. The biggest constituent(成分股，组成部分), Nvidia, accounts for(占……比例，解释) 8% of its value. Imagine the $5.3trn chip-designer’s share price moves up or down by 3% (as has happened 30 times this year) and the other 499 stocks are flat. The index then shifts by 0.25% in the same direction. No single name in the S&P 500’s history has packed a bigger punch(产生更大的影响).
以标普500为例。最大的成分股英伟达占其市值的8%。想象一下，这家5.3万亿美元的芯片设计公司的股价上下波动3%（今年已经发生了30次），而其他499只股票持平。那么指数就会朝同一方向变动0.25%。在标普500的历史上，还没有哪一只股票产生过如此大的影响。