Suppose there are two big$-$box retailers of equal size with employees who have identical job descriptions. One of the retailers, Oh$-$Dale Mart, pays its employees $$20$ per hour, has no air conditioning in their stores, and locates its stores in remote areas. Meanwhile, Ten Oaks Shoppe only pays its employees $$12\mathrm{.}50$ per hour but has air$-$conditioned facilities and locates its stores in easy$-$to$-$get$-$to suburbs. Which of the following is a plausible explanation for the difference in the wages of employees at $$h$-$Dale Mart and Ten Oaks Shoppe?