Meaning of PERCENTAGE in English
BAD : Only a small percentage of the windmills still works.
GOOD : Only a small percentage of the windmills still work.
If the noun after percentage of is plural, the verb is plural: 'A high percentage of these school leavers have no qualifications.'
Longman Common Errors English vocabulary. Английский словарь распространенных ошибок Longman. 2012