Which of the following is an accurate summary of the Will Rogers effect?
a. When the Okies left Oklahoma and moved to California, they raised the average intelligence level in both states.
b. When the Okies left Oklahoma and moved to California, they lowered the average intelligence level in both states.
c. When the Okies left Oklahoma and moved to California, they raised the residential segregation in both states.
d. When the Okies left Oklahoma and moved to California, they raised the average income level in both states.