A firm can vary supply of product by controlling a combination of the following two factors:
- Production capacity
In general, companies use a combination of varying capacity and inventory to manage supply. In the following sections, we list some specific approaches that allow firms to reduce the amount of capacity and inventory required to deal with predictable variability.
1. Managing Capacity
Firms use a combination of the following approaches to reduce the cost of capacity required to meet predictable variability:
- Time flexibility from workforce: In this approach, a firm uses flexible work hours by the workforce to vary capacity with demand. In many instances, plants do not operate continuously and are left idle during portions of the day or week. Therefore, spare plant capacity exists in the form of hours when the plant is not operational. For example, many plants do not run three shifts, so the existing workforce could work overtime during peak periods to produce more to meet demand. The overtime is varied to match the fluctuation in demand. In such settings, use of a part-time workforce can further increase capacity flexibility by enabling the firm to put more people to work during peak periods. This system allows production from the plant to match demand from customers more closely.
- Use of seasonal workforce: In this approach, a firm uses a temporary workforce dur ing the peak season to increase capacity to match demand. The tourism industry often uses seasonal workers. A base of full-time employees exists, and more are hired only for the peak season. Toyota regularly uses a seasonal workforce in Japan to match supply and demand better. This approach may be hard to sustain, however, if the labor market is tight.
- Use of dual facilities—specialized and flexible:In this approach, a firm uses both specialized and flexible facilities. Specialized facilities produce a relatively stable output of products over time in an efficient manner. Flexible facilities produce a widely varying volume and variety of products, but at a higher unit cost. For instance, an electronics component manufacturer might have specialized facilities for each type of circuit board as well as a flexible facility that can manufacture all types of circuit boards. Each specialized facility can produce at a relatively steady rate, with fluctuations being absorbed by the flexible facility.
- Use of subcontracting: In this approach, a firm subcontracts peak production so inter nal production remains level and can be done cheaply. For such an approach to work, the subcontractor must have flexible capacity and the ability to lower cost by pooling the fluctuations in demand across different manufacturers. Thus, the flexible subcontractor capacity must have both volume (fluctuating demand from a manufacturer) as well as variety (demand from several manufacturers) flexibility to be sustainable. For example, most power companies do not have the capacity to supply their customers with all the electricity demanded on peak days. They rely instead on being able to purchase power from suppliers and subcontractors that have excess electricity. This allows the power companies to maintain a level supply and, consequently, a lower cost.
- Designing product flexibility into the production processes:In this approach, a firm has flexible production lines whose production rate can easily be varied. Production is then changed to match demand. Hino Trucks in Japan has several production lines for different product families in the same plant. The production lines are designed so that changing the number of workers on a line can vary the production rate. As long as variation of demand across different product lines is complementary (i.e., when one goes up, the other tends to go down), the capacity on each line can be varied by moving the workforce from one line to another. Of course, this requires that the workforce be multiskilled and able to adapt easily to being moved from line to line. Production flexibility can also be achieved if the production machinery is flexible and can be changed easily from producing one product to producing another. This approach is effective only if the overall demand across all the products is relatively stable. Several firms that produce products with seasonal demand try to exploit this approach by carrying a portfolio of products that have peak demand seasons distributed over the year. A classic example is that of a lawn mower manufacturer that also manufactures snowblowers to maintain a steady demand on its factory throughout the year.
2. Managing inventory
Firms use a combination of the following approaches to reduce the level of inventory required to meet predictable variability:
- Using common components across multiple products:In this approach, a firm designs common components to be used in multiple products. The total demand of these components is relatively stable, even though each product displays predictable variability. The use of a common engine for both lawn mowers and snowblowers allows for engine demand to be relatively stable even though lawn mower and snowblower demand fluctuates over the year. Therefore, the part of the supply chain that produces components can easily synchronize supply with demand, and a relatively low inventory of parts has to be built up.
- Build inventory of high-demand or predictable-demand products:When most of the products a firm produces have the same peak demand season, the previous approach is not feasible. In such an environment, it is best for the firm to build products that have more predictable demand during the off-season, because there is less to be learned about their demand by waiting. Production of more uncertain items should take place closer to the selling season, when demand is more predictable. Consider a manufacturer of winter jackets that produces jackets both for retail sale and for the Boston police and fire departments. Demand for the Boston police and fire jackets is more predictable; these jackets can be made in the off-season and stocked up until winter. The retail jackets’ demand, however, will likely be better known closer to the time when they are sold, because fashion trends can change quickly. Therefore, the manufacturer should produce the retail jackets close to the peak season, when demand is easier to predict. This strategy helps the supply chain synchronize supply and demand better.
Next, we consider actions a supply chain can take to improve profitability by managing demand.
Source: Chopra Sunil, Meindl Peter (2014), Supply Chain Management: Strategy, Planning, and Operation, Pearson; 6th edition.