基于一些尚未明确的原因 — — 不利的人口趋势，较低的投资需求或是任何其他可能的解释，发达经济体都出现了生产率放缓的情况。
This productivity slowdown has occurred across advanced economies, for reasons – adverse demographic trends, lower investment demand, or any of a slew of other possible explanations – that remain unclear.