A discrimination case compared the 1976 salaries of Georgia Power Company black and white employees who had been hired by the company in 1970 to similar entry-level positions [24].

a. Explain why there is survivor bias in this comparison.

b. Suppose that there are two types of employees, productive and unproductive, and that Georgia Power hired 100 black employees and 100 white employees in 1970 at the exact same salary, with half the new hires productive and half unproductive, regardless of race. Each year, every unproductive employee got a 2 percent annual raise and every productive employee got a 7 percent annual raise. Explain how it could still turn out that the average salary of white employees in 1976 was higher than the average salary of black employees.