In an investigation of the relationship between the unemployment rates and aggression rates in San Francisco, researchers found all of the following EXCEPT that

a. violence increased as unemployment increased, but only up to a certain point.
b. fears of losing their own jobs may have led some people to inhibit frustration-driven violence.
c. when unemployment was too high, the level of violence fell again.
d. under all circumstances, the higher the unemployment, the higher the level of violence.

Answer: d. under all circumstances, the higher the unemployment, the higher the level of violence.