这一信心持续缺失的唯一符合逻辑的解释，正如西北大学的罗伯特·戈登（Robert Gordon）费煞苦心地记录和论证的，是生产率增长缓慢。
The only logical explanation for this enduring lack of confidence, as Northwestern University’s Robert Gordon has painstakingly documented and argued, is slow productivity growth.