percent, percentage

Always expressed in figures except one percent.

Do not hyphenate compound adjectives with percent:

Write out percent in text. The percent symbol may be used in fact boxes and in map notes.

Percent may be singular or plural depending on the intention of the writer.  Generally the object of the preposition of  following percent and percentage governs the verb:

            10 percent of the population is illiterate

            10 percent of the people are illiterate

8 percent reduction

11.75 percent

1.2 percent

0.5 percent

.33 percent

3,000 percent

100 percent