Answer:The labor demand schedule has a negative slope due to the operation of the law of diminishing marginal productivity and the profit-maximizing behavior of firms. The law of diminishing marginal productivity states that as more units of a variable input, such as labor, are added while other inputs are held constant, the additional output or productivity gained from each additional unit of the variable input will eventually decrease. In the context of labor, this means that the marginal product of labor declines as more workers are employed.