谁帮忙翻译一下这个短语 The baseline position

谁帮忙翻译一下这个短语 The baseline position
谁帮忙翻译一下这个短语：
The baseline position
肯定不是直接翻译,应该是个俗语什么的吧,谢谢了先.
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For example, PARS is putting this into practice for the world's largest mail company, the United States Postal Service (USPS).

The baseline position(原文这里是加重的，感觉向标题一样)
The USPS serves one of the most mobile markets in the world, with about 17 per cent of US citizens moving house every year. This resulted in 40 million address changes in 2001 alone. The number of wrong deliveries caused by out-of-date addresses being used is correspondingly high, with 1.3 billion letters being returned to sender each year. That means high costs for the postal service and the annoyance of late deliveries for their customers.
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