The ratio of indigenous-to-foreign labor in the Gulf

Solution

We need a verb to be modified by the adverb HIGHLY. The sentence seeks to convey that the ratio of indigenous-to-foreign workers in the Gulf states is not uniform. IMBALANCED and SKEWED fit contextually. If you describe a situation as IMBALANCED, you mean that the elements within it are not evenly or fairly arranged. SKEWED means non-uniform. PROPORTIONAL (corresponding in size or amount to something else) and COMMENSURATE (corresponding in size or degree) are synonyms. They do not fit contextually. UNIFORM (remaining the same in all cases and at all times; unchanging in form or character)conveys the opposite meaning. UNILATERAL ((of an action or decision) performed by or affecting only one person, group, or country involved in a situation, without the agreement of another or the others) does not fit contextually.