Planning Strategies

The aggregate planner must make trade-offs among capacity, inventory, and backlog costs. An aggregate plan that increases one of these costs typically results in reduction of the other two. In this sense, the costs represent a trade-off: To lower inventory cost, a planner must increase capacity cost or delay delivery to the customer. Thus, the planner trades inventory cost for capacity or backlog cost. Arriving at the most profitable combination of trade-offs is the goal of aggregate planning.

The fundamental trade-offs available to a planner are among the following:

• Capacity (regular time, overtime, subcontracted)
• Inventory
• Backlog/lost sales because of delay

There are essentially three distinct aggregate planning strategies for achieving balance among these costs. These strategies involve trade-offs among capital investment, workforce size, work hours, inventory, and backlogs/lost sales. Most strategies that a planner actually uses are a combination of these three and are referred to as tailored or hybrid strategies. The three strategies are listed below.

Chase strategy

It uses capacity as the lever. With this strategy, the production rate is synchronized with the demand rate by varying machine capacity or hiring and laying off employees as the demand rate varies. In practice, achieving this synchronization can be problematic because of the difficulty of varying capacity and workforce on short notice. This strategy can be expensive to implement if the cost of varying machine or labor capacity over time is high. It can also have a significant negative impact on the morale of the workforce. The chase strategy results in low levels of inventory in the supply chain and high levels of change in capacity and workforce. It should be used when the cost of carrying inventory is high and costs to change levels of machine and labor capacity are low.

Flexibility strategy

It uses utilization as the lever. This strategy may be used if there is excess machine capacity (i.e., if machines are not used 24 hours a day, seven days a week) and the workforce shows scheduling flexibility. In this case, the workforce (capacity) is kept stable, but the number of hours worked is varied over time in an effort to synchronize production with demand. A planner can use variable amounts of overtime or a flexible schedule to achieve this synchronization.

Although this strategy does require that the workforce be flexible, it avoids some of the problems associated with the chase strategy—most notably, changing the size of the workforce. This strategy results in low levels of inventory but with lower average machine utilization. It should be used when inventory carrying costs are relatively high and machine capacity is relatively inexpensive.

Level strategy

It uses inventory as the lever. With this strategy, a stable machine capacity and workforce are maintained with a constant output rate. Shortages and surpluses result in inventory levels fluctuating over time. In this case, production is not synchronized with demand. Either inventories are built up in anticipation of future demand or backlogs are carried over from high- to low-demand periods. Employees benefit from stable working conditions.

A drawback associated with this strategy is that large inventories may accumulate and customer orders may be delayed. This strategy keeps capacity and costs of changing capacity relatively low. It should be used when inventory carrying and backlog costs are relatively low. In practice, a planner is most likely to come up with a tailored or hybrid strategy that combines aspects of all three approaches.