1. The busiest port by passenger volume is the Port of Miami in the U.S.
  2. The busiest port in passenger volume is the Port of Miami in the U.S.
  3. The busiest port in terms of passenger volume is the Port of Miami in the U.S.

About the choice of prepositions in the case, I don't know why by is correct. I tend to choose in, meaning in terms of.

Is there a general rule here?

2 Answers 2


We use 'by' when ranking things when we wish to make clear what criterion we are ranking by. XXX is the busiest port by passenger numbers, but YYY is the busiest by ship movements. The largest animal by height is the giraffe; by weight, the elephant.


All three are idiomatic in this context, since, as you say, "in" is interpreted to be short for "in terms of". However I think this is more about accurate communication and good style than about any particular rule. For example, this sentence:

The largest land animal by/in terms of weight is the African elephant

"The largest land animal in weight" sounds a little awkward to me, although oddly enough I would be fine with:

The African elephant is the largest animal in weight.

I think the reason is that the sentence might be misunderstood if spoken, as a listener might initially think "weight" is a place name:

The Isle of Wight lies off the coast of Hampshire, England. The largest native land animal in Wight is the red squirrel.

You can see how "in weight" might cause confusion, so it's more helpful to write out "in terms of" instead of just "in". In your example sentence, no one would normally confuse "passenger volume" with a place name, so it's fine.


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