Answer: Education.
Explanation: Economic downturn, politics and technology change are factors that affect income that is not within a workers control. The workers can’t single handedly control economic downturn , politics of the nation is another factor that is not within the jurisdiction of the workers which can affect the income, lastly technological change is completely out of the workers control, they have no power over it.
However, Education is the only only factor that can affect workers income that is within the workers control, in a nutshell , a worker willing to get improvement in his or her income is expected to seek more knowledge (education) to improve his skills and he can command more income as a result.
