India’s income per head, for example, was about $3, 200 in 2009 (holding purchasing power constant across time and between countries).

例如，印度的人均收入在2009年大约是3200美元（不管是跟以往相比还是各国家之间，购买力都没变。）

youdao

Nevertheless, the value of money is not constant over time. The purchASing power of money changes AS a result of either inflation or deflation.

但货币的价值并不总是稳定不变的，货币的购买力会随着通货膨胀或通货紧缩而产生变化。

youdao

However, money serves its function as a standard of deferred payment only if its purchasing power remains fairly constant over time.

可是，只有在金钱的购买力在一段时间内保持相对稳定的条件下，金钱才能起到赊账延期支付标准的作用。

youdao

The assumption is that if African purchasing power remains relatively constant over the next few years and the cost of imported replacement weapons remains significantly higher than the cost of the old stuff, total numbers will decline over time.

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