Sentence:  Accordingly , maturity level ratings by means of the upper portion and lower portion of the Chart , respectively , should be somewhat similar since Skeletal Age assessments <WSD>are</WSD> dependent upon Onsets during infancy and upon Completions during adolescence . 
Meaning of the word marked with <WSD> tags:  have the quality of being; (copula, used with an adjective or a predicate noun)