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percent, percentage

Always expressed in figures except one percent.

Do not hyphenate compound adjectives with percent:
8 percent reduction
11.75 percent
1.2 percent
0.5 percent
.33 percent
3,000 percent
100 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