Performance optimization multipliers
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Can anyone provide an example of a system in which a performance improvement of x% to a single sub-component of the system results in an overall performance increase of Ax% (where A>1) for the entire system?  In other words, can there be a positive multiplier effect for localized optimizations in a system?  

I could have sworn that I have encountered such performance multiplier effects in the past, but for the life of me, I cannot construct even a hypothetical example of such a case.
