经济学家迈克尔·赫德森的研究揭示了这个体系更深的逻辑：各国之所以“不得不”持有美元、买入美债，是因为整个国际贸易体系是被强制性地用美元计价的——首先是石油，然后是大宗商品，然后逐渐蔓延到几乎所有重要的国际贸易品。
Beyond that, there's the spending plans the chancellor has pencilled in for future years. The rate of growth of public spending slows down in a few years' time. Take account of population growth and inflation and some departments' budgets may be squeezed.
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sequenceDiagram
Green: Put your thinking cap on!
const realIdx = i % len; // 取模映射到真实数组索引，模拟循环