Paraphrasing is to use different words with the same meaning. However you have inverted the meaning.

"The Will Rogers phenomenon is obtained when moving an element from one set to another set raises the average values of both sets. It is based on the following quote, attributed (perhaps incorrectly) to comedian Will Rogers:

When the Okies left Oklahoma and moved to California, they raised the average intelligence level in both states.

The effect will occur when both of these conditions are met:

The element being moved is below average for its current set. Removing it will, by definition, raise the average of the remaining elements.
The element being moved is above the current average of the set it is entering. Adding it to the new set will, by definition, raise the average."

If you haven't noticed, this is a definition in the branch of mathematics called set theory.

These days the reference is usually made to those leaving California. In actuality the difference is not intelligence but age. Younger people are moving to California for jobs, usally in technical fields. Older people (especailly retirees) are moving from California seeking a lower cost of living.