This is a typical case for Expressions of quantity. There is no exact rule or exact verb to be used in these scenarios. It specifically depends on the noun or clause with which it has been used. If the noun is singular, then it's singular, and if the noun is plural, then it's plural.
SingularHalf of
the truth is known.
Half of
what he writes is undocumented.
PluralOnly about half of
the students believe the truth
Half of
his articles are peer reviewed.
My personal suggestion would be to carefully observe the sense of this expression of quantity like 'fifty percent', 'one third', 'half', etc. If the sense suggests plural, use a plural verb else go for a singular one.