Econ Papers Daily / 期刊论文
繁殖延迟决定猪周期的波长
Breeding delays determine the wavelength of the pork cycle
摘要
The pork cycle exhibits persistent oscillations in prices and production with a wavelength of three to six years. We develop a system dynamics model in which cyclical behaviour arises endogenously from biological delays and a simple adjustment rule, without the explicit modelling of price or forward-looking optimization from decision-makers. The model reproduces the cyclical component of Dutch pork prices, matching its wavelength and turning points, and explains the gradual shortening of the cycle through technological changes that reduced production lead times. Sensitivity analysis further separates the parameters that govern the cycle’s wavelength from those that govern its amplitude, and identifies policy levers acting on each. Our findings do not imply that prices are irrelevant; rather, they highlight that a significant part of the pork cycle is structural, with prices primarily reflecting underlying production delays. This perspective complements rational-expectations models and clarifies why similar ‘pork cycle’ patterns appear in other industries with long lead times.
中文摘要
猪肉周期在价格和产量上表现出持续振荡，波长为三至六年。我们构建了一个系统动力学模型，其中周期性行为由生物学延迟和简单的调整规则内生地产生，而未显式建模价格或决策者的前瞻性优化。该模型再现了荷兰猪肉价格的周期性成分，与其波长和转折点相匹配，并解释了通过缩短生产提前期的技术变革所导致的周期逐渐缩短。敏感性分析进一步区分了决定周期波长的参数与决定其振幅的参数，并识别出分别作用于二者的政策杠杆。我们的发现并不意味着价格无关紧要；相反，它们强调猪肉周期的很大一部分是结构性的，价格主要反映潜在的生产延迟。这一视角补充了理性预期模型，并阐明了为何在其他具有长提前期的行业中也出现类似的“猪肉周期”模式。