16) How does the demand for high-skilled workers compare to the demand for low-skilled workers? Why does this difference exist? 17) At any wage rate, the quantity of welders willing to work is less than the quantity of tomato pickers. Why? 18) Describe the effect education and training have on outcomes in the labor market. 19) What factors explain why high-skilled workers are paid more than low-skilled workers? 20) Some economists argue that discrimination based on race and sex cannot lead to persistent wage differentials. What is their argument?