With words that indicate portions—'percent, fraction, part, majority, some, all, none, remainder' —look at the noun that is the object of the preposition 'of' to determine whether to use a singular or plural verb. If the noun is singular, use a singular verb. If plural, use a plural verb.
Fifty percent of the pie has disappeared.
"pie" is the object of the preposition 'of', and 'pie' is singular.
Fifty percent of the pies have disappeared.
"pies" is the object, and plural.
One-third of the city is unemployed.
One-third of the people are unemployed.
All of the pie is gone.
All of the pies are gone.
Some of the pie is missing.
Some of the pies are missing.
None of the garbage was picked up.
None of the sentences were punctuated correctly.
Of all her books, none have sold as well as the first one.