You will be shown an excerpt from a computer science scientific research paper, followed by a question about the paper. Please answer the question. Do not include any text in your response other than the answer.

Context: Wordpieces achieve a balance between the flexibility of characters andefficiency of words.We also find that our models get better overall BLEU scores when usingwordpieces – possibly due to the fact that our models now dealefficiently with an essentially infinite vocabulary without resorting tocharacters only. The latter would make the average lengths of the input and outputsequences much longer, and therefore would require more computation.

Question: How can the limited set of common sub-word units (“wordpieces”) provide a good balance between the flexibility of “character”-delimited models and the efficiency of “word”-delimited models?
Authors assume that's due to the fact that it deals efficiently with an essentially infinite vocabulary without restoring to characters only.