What does disproportionately means?
I know it means too large or too small in comparison with something else but how do I know is it too large or too small?For example, countries still trade disproportionately with their geographic neighbours. (the ans is too large; how do they know it?)[FULL PARAGRAPH: Countries still trade disproportionately with their geography neighbours. Over time, however, world output has shifted into goods whose worth is unrelated to their size and weight. Today, it is finish manufactured products that dominate the flow of trade and thanks to technological advances such as light weight compliments, manufactured goods themselves have trying to become lighter and less bulky. As a result less transportation is required for every dollar's worth of import or export.]

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Did you copy that paragraph incorrectly? Or was it written by a non-native speaker? The English has many mistakes.
As far as the question goes - you can't tell from the words. You have to infer it from the meaning. 
The key word is 'still' - referring to the fact that historically countries would have primarily traded with their neighbours. If there is still a disproportionality, you can assume from the 'still' that it is slanted the same way it was historically.

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In this paragraph, 'disproportionate' refers to an imbalance of trade, with one country exporting or importing more than it sends to, or receives from, its trading partners.