The national-income accounts double-count investment, which enters once when it occurs and again in present value as rental income on added capital. The double counting implies that GDP and national income overstate sustainable consumption. An alternative measure, ‘permanent income’, equals consumption in the steady state but deviates from consumption outside of the steady state because expensing of gross investment applies to the long-run flow, not the current value. The permanent-income perspective substantially affects measured factor-income shares. When computed in relation to permanent income, the US labour-income share has been reasonably stable, in contrast to the declining share based on GDP.

中文翻译：

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重复计算投资

国民收入账户重复计算投资，投资在发生时计入一次，然后以现值作为新增资本的租金收入。重复计算意味着 GDP 和国民收入高估了可持续消费。另一种衡量标准，“永久收入”，等于稳定状态下的消费，但偏离稳定状态外的消费，因为总投资的费用适用于长期流量，而不是当前价值。永久收入的观点极大地影响了衡量的要素收入份额。当与永久收入相关时，美国的劳动收入份额相当稳定，与基于 GDP 的份额下降形成鲜明对比。