Final answer:
The worker productivity increase at de Castellane Manufacturing Company is primarily due to a profit-sharing plan that has motivated employees by tying their bonuses to company profits, leading to improved productivity.
Step-by-step explanation:
The increase in worker productivity at the de Castellane Manufacturing Company is best explained by the introduction of a profit-sharing plan, where employees receive semiannual bonuses based on the company's profits. This type of incentive aligns employees' interests with the success of the business, resulting in improved productivity. Additionally, when a company invests in technology or machinery, it can lead to heightened productivity as workers are able to leverage better physical capital equipment. However, this may also result in the need for fewer employees due to increased operational efficiency.