My wife heard this two days ago on NPR.

Problem:
The speaker used an adjective where an adverb was required.

Explanation:
National Public Radio on March 12 aired a report in which my wife heard someone say, “Women are still not paid equal to men.”

As is true for “naked” verbs, the passive-voice construction “are still not paid” may be modified by an adverb but may never be modified by an adjective.

The word “equal” is an adjective, not an adverb.

Many adjectives — including “equal” — can be converted into adverbs by adding the “ly” suffix.

I believe that the omission of the “ly” suffix from what should be the adverbial forms of adjectives is consistent with my “Devolution toward Simpler” linguistic hypothesis.

It is simpler to omit the “ly” suffix, which adds two more letters and an extra syllable, than to include it.

Solution:
“Women are still not paid equally to men.”