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12 5 Prediction Intervals For Aggregates

September 6, 2023
Bill Kimball

In considering these studies, we see a more palatable approach to overcoming these challenges. Namely, repeated interactions between decision makers elicit a greater aversion to lying, resulting in significant reductions in forecast error, even without financial incentives. During the period of study, the research site introduced a disaggregated demand forecast system. The new system established a reporting tool for sales managers to disaggregate the demand forecast for each product into two parts. The first part was a forecast of expected sales from relatively predictable demand sources (e.g., repeat sales to customers).

aggregate forecast vs disaggregate forecast

Disaggregation can help reduce the cognitive load on the decision maker, helping the individual focus on the most relevant cues for the prediction. Forecasts are generally more accurate the closer they are to the current period. It also follows that forecasts are less accurate for farther periods of time. In other words, the accuracy or quality of the forecast decreases as we move further down the time horizon into the future. My question is coming up with an accurate predictive forecast based on forecasting individual component parts, then adding then up …

Fundamental Rules Of Forecasting

Still, despite the extensive costs and acknowledgments for a need to improve, significant progress in forecast accuracy remains elusive for many companies. In many settings, self-interested sales managers have incentives to generate positively biased demand forecasts. They want to influence production decisions with the objective of ensuring adequate inventory for the specific products and services they anticipate selling. The lack of transparency in an aggregate demand forecast provides sales managers increased opportunity to introduce opportunistic positive bias as a means of influencing production decisions in their favor . Demand forecasting is a critical management process affecting the planning and coordination efforts between commercial, supply chain, and finance functions.

aggregate forecast vs disaggregate forecast

For example, managers may struggle to attend to all demand information. They may overly rely on their recall of recent sources of demand, or perhaps sources of demand that loom the largest, and neglect sources of demand that are sporadic or smaller in magnitude.

The Perfect Forecast Level: Bottom Up Or Top Down?

Under this strategy, the company maintains steady production levels and allows inventory levels to vary from month to month. During certain periods, the company will develop overstock that it can either store or attempt to sell through promotions and price reductions. At other times, the strategy might lead to temporary shortages and backorders.

After being lauded for the accuracy and speed of its estimates without the need for human judgment, the model, called Google Flu Trends , failed dramatically in the 2013 flu season, missing the peak estimates by 140%. These fundamental rules are fairly basic and it is usually intuitively clear that these hold true. On their own however, they do not allow us to understand which forecast level should be used in any given situation. The level of aggregation depends on the data and purpose of the forecast. Nakul started his career in Arkieva in July 2014, joining the consulting team. His work experience includes a brief stint in a brakes manufacturing company followed by consulting experience in service parts planning services and operational analytics. In Arkieva, he has been implementing Demand & Inventory Planning solutions for clients.

Whenever a firm “builds to anticipation” they face the risk the demand will never materialize. In services you cannot build product to anticipated sales so this will require tools such as reservations and appointments with a heightened sensitivity to seasonal spikes. In contrast using a chase model in the tangible world requires adjusting capacity to demand to include hiring/firing of human resources. Following this path has a direct impact on quality as well as an indirect cost to the business. Finally, subcontracting potentially requires the sharing of sensitive information. The firm must carefully weigh out the risks and rewards of such a venture.

But these types of incentive schemes are uncommon in practice, likely because many organizations worry about sales managers misallocating their effort toward forecast accuracy at the expense of revenue generation. Finally, the research also revealed that the decline in finished goods inventory was accompanied by an increase in work-in-process inventory. Importantly, this shift from finished goods to work-in-process wasn’t accompanied by an increase in costly last-minute production plan changes. The results indicate that the disaggregated demand forecast system facilitated a production “postponement” strategy where final manufacturing and packaging of the product are delayed as long as possible.

aggregate forecast vs disaggregate forecast

Multiple weaker hierarchies can be combined using regression or other approaches to optimize the overall prediction at every level. Now if I adjust the product family level forecast, the following steps are followed in a planning system to adjust detail level i.e. product level forecast. Our findings suggest that disaggregation can be a useful tool in the pursuit of forecast accuracy improvements, but there are several factors to consider for implementation. For example, if a disaggregated process increases the number of steps so much so that task complexity is increased, the disaggregation will actually increase cognitive load and will likely decrease judgment quality. Conversely, disaggregating a relatively simple task may be more trouble than it’s worth as the benefits of disaggregation are greatest with more complex tasks (see “Effective Use of Disaggregation”).

Youll Often Need Multiple Levels Of Aggregation

The key for any model is to insure delivery to the customer while minimizing costs. Service business’ are included in these examples and in fact are more complex. Level loading using seasonally adjusted forecasts in a tangible environment will require building inventory in advance of demand.

  • The increased transparency of disaggregated demand forecast information can discipline sales managers and reduce opportunistic positive forecast bias.
  • The total forecast at product family level and per product from Jan-18 to Jun-18 is given in the table.
  • Finally, subcontracting potentially requires the sharing of sensitive information.
  • Under this strategy, the company maintains steady production levels and allows inventory levels to vary from month to month.
  • Researchers investigating the failure found that GFT was vulnerable to overfitting to limited sets of data points and was slow to take into account changes in user search behavior over time.
  • Suppliers even adjust their customer support based on the quality of forecasts they receive.
  • During the period of study, the research site introduced a disaggregated demand forecast system.

Or we may have weekly data, and want to forecast the total for the next four weeks. After you have considered the ins and outs and process in between, you should always attempt to forecast at the highest level of aggregation compatible with the process and decisions goals.

Managing this effectively can maximize your resources used while improving the forecast the business uses. Total Forecast for the product family is nothing but the sum of detail level forecasts which is equal to 4,750. Similarly, the Total Forecasted Revenue at the product family level is 35,550. In demand planning terminology, Forecast Reconciliation is also referred to as Bottom-up and Top-down Forecasting or Proportional Forecasting. Forecast Reconciliation, however, could also stand for reconciling the demand forecast with a modeled forecast vs. a judgmental forecast or a financial forecast. A common problem is to forecast the aggregate of several time periods of data, using a model fitted to the disaggregated data. For example, we may have monthly data but wish to forecast the total for the next year.

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Aggregating data for forecasts is one of topics that will be discussed at IBF’s Boston Academy from August 12-13, the world’s leading training event for S&OP, Forecasting, Planning & Analytics. Among the value-added workshops is “How & When To Use Top down, Bottom Up, and Other Forecasting Approaches” delivered by Joe Eschenbrenner, Director Of Demand and Supply Planning at Puma.

How To Calculate The Inventory Needed

Sales, forecast, orders, revenue can be summed up whereas costs and price cannot be summed. To aggregate costs or prices, the average or weighted average should be used. Pete Papantos is an operations director at a Fortune 500 company. He is responsible for the global execution of their strategic plan and driving operational excellence using lean methods. In addition, Pete is a graduate instructor with emphasis in operations and strategic management — both in traditional and online settings.

Companies adjust labor hours in several ways, including hiring or laying off workers, changing the amount of overtime, and modifying the number or length of shifts. Some companies may be constrained from laying off workers because of corporate policy, while others don’t hesitate to cut staff as needed. Companies might hire temporary workers when the aggregate forecast predicts a labor shortage. In some cases, a forecast for higher demand might encourage a company to put a mothballed plant back into production and increase labor. Conversely, a loss of market share might prompt the company to close a plant and lay off the work force. Successful companies are forever planning ahead, because they need lead time to prepare for implementing their plans.

What Is An Aggregate Forecast?

An aggregate forecast addresses a company’s capacity requirements — the amount of product it needs to produce and strategies for producing it — for the period two to 12 months in the future. A company can set or reset strategy in this period and synchronize activities that affect costs, resource allocation, capacity utilization, labor requirements and customer relations.

So the lower the level, the more difficult it becomes to create any useful statistical model because of sketchy and intermittent demand data. If that is the case, forecasting at the SKU/customer level will magnify the impact of noise and data infrequency. Forecasting at the customer SKU level also means aggregating not only at the customer SKU to the SKU level, but also aggregating all the way to the top, to the division level. For example, in top-down forecasting, a company-level sales forecast broken down into a category level, or a category-level forecast broken down into a SKU level. When I adjust my product family level forecast to 140 the forecast of P2 changes from 50 to 58 which is nothing but ~ 42% of 140. When you develop your forecasting process, you have a choice to make – at what level do you develop the forecast?

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