根据住宅建筑支出的序列分析，许多经济学家已经注意到存在长达20年的“建筑周期"现象。你能为这些大

周期做出一个与加速数模型类似的解释？ Many economists have noted the existence of“building cycles”of roughly 20 years’durationbased on series for expenditures on residential construction．Can you suggest an acceleratorlike explanation ior these long cycles？