Bill Gross, the so-called “Bond King,” thinks stocks are currently "priced for too much hope," and here's why: He doubts President Trump can deliver rapid economic growth because the United States simply isn’t as productive as it used to be.

“High rates of growth, and the productivity that drives it, are likely distant memories from a bygone era,” he notes in his monthly investment outlook released Thursday morning.

Gross, who rose to prominence as a star bond investor with Pimco, is now a fund manager with Janus, and his sometimes clever, tongue-in-cheek monthly newsletters have a wide following.

This month the newsletter starts with a rather grotesque brainteaser. (Gross asks: “If forced to choose between killing your favorite pet or an anonymous human being, what would you do?”)

But then he dives into the real-life conundrum currently facing economists and policymakers: An important ingredient of economic growth has stalled in recent years, and it’s still a mystery as to why.

Known as total factor productivity, it’s essentially a measure of how efficient workers and capital are in producing services and products. Improvements in technology, education, and even public health can factor into this somewhat ambiguous, but crucial variable for developed economies.

The pessimists in the debate, like Northwestern University economist Robert Gordon, have argued that the best days for the U.S. economy may be behind us, after we already picked the “low hanging fruit” of massive technological improvements like electrification, indoor plumbing, the automobile, jet engines and the Internet. Optimists, meanwhile, argue we cannot foresee the technological improvements of the future, which may still lead to strong economic growth.

Federal Reserve Chairwoman Janet Yellen touched on the debate earlier this week in a speech at the University of Michigan, noting that recently productivity has been “very disappointing,” despite stronger job growth.

“The fact that you can create that many jobs in the context of growth that is so low points to a significant problem,” she said. “And the problem is that productivity growth is very low.”

As with his brainteasers, Gross notes, “There is no right or wrong answer” for economists. But in his view, investors are relying too heavily on models based on history that may not repeat itself. And for this reason, stocks, high-yield bonds, and other asset prices are too high.

“Equity markets are priced for too much hope, high yield bond markets for too much growth, and all asset prices elevated to artificial levels that only a model driven, historically biased investor would believe could lead to returns resembling the past six years, or the decades predating Lehman,” Gross wrote.

享有“债券之王”美誉的比尔·格罗斯认为，股市“目前的定价太过依赖预期”，他的理由是，并不确信美国总统特朗普能推动经济迅速增长，因为美国的生产率不如以往。

“高增长率及其推动的生产力可能已成遥远的回忆，一去不返。”格罗斯在本周四上午发布的月度投资展望中如是说。

格罗斯曾因担任全球共同基金巨头太平洋投资管理公司（Pimco）的明星债券投资者蜚声业内，目前担任骏利资产管理集团基金经理。他时而睿智时而讽刺的月度投资展望广受欢迎。

本月的投资展望开头提出一个有点怪异的问题。（格罗斯问：心爱的宠物和一个不认识的人二选一，必须杀死一个，你会怎么选？）

但接下来，他深入剖析现实世界经济学家和决策者当前面对的难题：近年来经济增长的一大要素增长停滞不前，原因成谜。

所谓全要素生产率，实际上是指劳动力和资本转化为产品和服务的效率。对发达经济体而言，科技、教育、甚至公共卫生领域的进展都包含在全要素生产率中，有时可能体现得并不明显，但都十分重要。

在关于生产率的争论中，美国西北大学经济学家罗伯特·戈登等悲观人士认定，人们享用电气化、室内暖通、汽车、喷气式发动机和互联网等巨大科技进步“低垂的果实”后，美国经济的黄金岁月可能已经远去。而乐观人士认为，我们无法预见未来的科技进步，有可能科技发展还能继续推动经济强劲增长。

本周稍早，美联储主席珍妮特·耶伦在密歇根大学的演讲也提及这个话题。她当时指出，虽然就业增长强劲，但最近生产率“非常令人失望”。

耶伦说：“经济增长如此缓慢还能创造如此多就业，显示问题非常严重。说明生产效率增长很慢。”

格罗斯则借助投资展望里的烧脑问题指出，对经济学家来说，“答案不分对错。”可在他看来，投资者过于依赖根据历史表现编制的模型，但用过去预测未来并不一定准确。也正是基于已有估值，股市、高收益债券等资产的价格普遍太高。

格罗斯写道：“人们对未来的希望太美好，所以股市估值过高，对增长太乐观，所以高收益债券估值也不低，所有资产价格都炒高了。只有热爱估值模型，强烈依靠历史数据做判断的投资者会相信，今后还会出现过去六年、或者雷曼兄弟倒闭之前几十年里同样高额的回报。”（财富中文网）

译者：Pessy

审稿：夏林