Plurals and Possessives

Writers who make mistake the plural for a possessive once will often do so repeatedly. An occasional typo won’t trigger a Fails for Grammar, but pervasive errors will.
Incorrect: America is the worlds most obese nation.
Correct: America is the world’s most obese nation.
Correct: Earth is fine but there may be other worlds we could occupy.

The rule is only slightly more complicated when a plural is formed without an “s.”
Incorrect: Democracy is every citizens responsibility.
Incorrect: Democracy is the peoples’ responsibility.
Correct: Democracy is the people’s responsibility and every citizen’s privilege.
Correct: Democracy is strong when all citizens’ rights are observed.