Effective demand forecasting: an explanation of the methods and their application.

Any company that manufactures goods and requires materials to produce its end products must take account of its material requirements. What are the respective material requirements, and what demand for products, spare parts and saleable intermediate goods can you expect in the future? Accuracy is essential here to ensure that production does not come to a standstill.

The solution lies in demand forecasting, for which various mathematical and statistical methods are also used. Which types of demand are necessary and appropriate, what methods of demand forecasting are available, and how can you apply them in practice? We provide key definitions and clarify these questions in our article.

Key points at a glance:

  • By carrying out a requirements analysis, you can ensure that you always order the correct quantity of parts and materials. This helps you avoid both shortages and surpluses.
  • You can distinguish between different types of requirements. These include primary, secondary, tertiary, gross and net requirements.
  • There are various methods available for determining requirements. Among the most important are programme-based and consumption-based requirements analysis.
  • With an ERP system such as collana diva now, you can optimise demand planning and materials management.

What is a needs assessment?

By definition, demand forecasting is a business management process that companies carry out to determine their requirements. In materials management, demand forecasting is one of the most important methods, as it ensures the company’s supply of materials and identifies future material requirements. By definition, demand forecasting is also known as demand quantity planning, material requirements planning and procurement planning.

Why is demand forecasting so important for businesses?

Because it helps to optimise costs and storage space. When it comes to material procurement, precision is essential to avoid both overstocking and understocking. This applies equally to goods, spare parts, saleable semi-finished products or assemblies, and production materials. In other words: determining demand forms the basis for all procurement strategies.

It is not only procurement that benefits from this analysis, but also production. What raw materials, semi-finished products, assemblies and individual parts do you need to complete orders or keep production running?

Here’s an example: A company manufactures wooden garden benches. In this case, it makes a real difference whether the requirement is for 2 tonnes of wood, 12,000 screws and 30 litres of oil, or whether you only need 1 tonne of wood and 4,000 screws. An order for 4 tonnes of timber and 16,000 screws would, in fact, be an over-order, which incurs storage costs and ties up capital. Ordering too little, on the other hand, causes supply bottlenecks.

Needs assessment: Breakdown by the following types of needs

Before we move on to the methods for assessing needs, it is first necessary to categorise them according to the following types of need:

  • Primary needs: Primary goods are finished products and services that you sell directly to customers. These include, for example, finished cars, pyjamas, spare parts or wooden benches.
  • Secondary requirements: This includes all raw materials and components required for the production of essential goods or to fulfil firm customer orders. Examples include car tyres or windscreens, buttons for pyjamas, and wooden slats for a wooden bench.
  • Tertiary requirements: Although these materials are not directly incorporated into the end product or counted as primary requirements, you do need them to manufacture the product. These include operating and auxiliary materials (e.g. lubricants for machinery).

This distinction between primary, secondary and tertiary requirements is based on the materials you need at each stage of production. In addition, you can distinguish between two further types of requirement:

  • Gross requirement: This figure is obtained by adding together the secondary and tertiary requirements. It therefore represents the total requirements needed to manufacture the product.
  • Net requirement: This, on the other hand, refers to materials which you still need to procure or manufacture. The figure is calculated by subtracting the available stock from the gross requirement.

Available stock = +Stock -Reserved materials +Open purchase orders and production orders -Safety stock
Net requirement = Gross requirements – available stock

Overview: Methods for assessing needs

There are various techniques used in demand forecasting. In addition to estimates, you can, for example, obtain some figures directly from ERP software. Various mathematical and statistical methods are also used. The following methods are available for demand forecasting:

1. Programme-based needs assessment (deterministic method)

This method is based on current production plans and bills of materials. Primary requirements are determined by existing orders and plans. Using these, you can then plan secondary and tertiary requirements, calculate the necessary auxiliary materials and resources, and determine the gross and net requirements.

2. Consumption-based demand forecasting (stochastic demand forecasting)

Under the consumption-based (stochastic) method, future requirements are determined on the basis of past consumption.

An example? For July and August, the method calculates a quantity based on previous consumption and possible forecasts. Mathematical statistical methods (stochastics) are used, which allow you to optimise the results. These are particularly useful when sales volumes fluctuate.

The key factor is the pattern of demand, which may be constant, trend-based, seasonal, sporadic or highly volatile.

3. Rule-based demand forecasting

Put simply, rule-based demand forecasting is an ‘if-then’ scenario. If a particular situation arises, a specific material requirement results. For example, if a customer orders a car with specific features, this creates a requirement for specific parts and materials (e.g. leather in an unusual colour, an on-board computer, etc.).

4. Subjective estimation (heuristic needs assessment)

If only limited historical data is available, you can estimate the expected demand. The estimate should then be based on empirical evidence and a certain level of expertise. However, this method is not recommended if another method is better suited to determining demand.

Advantages and disadvantages of methods for assessing needs

Each of these methods has its own advantages and disadvantages, which you should weigh up. We have therefore put together an overview of the key points below.

MethodAdvantagesDisadvantages
Programme-based needs assessmentLower stock levels, as production is carried out to orderReduced ability to fulfil orders, as production only begins once an order has been received
 High accuracy in determining requirements based on bills of materialsLonger lead times due to the procurement period
Consumption-based demand forecastingHigh delivery reliability and short lead times, as products are already in stockHigher warehouse utilisation, as production is geared towards the market
 Minimal effort required as calculations are based on historical figuresInaccurate stock figures due to historical data
Rule-based demand forecastingHigh cost-effectiveness thanks to standardised processesLow volatility, as seasonal changes or market fluctuations are not taken into account
 Easy to plan due to fixed parametersLimited adaptability
Subjective estimateMinimal effort, as no analyses and, in most cases, no data are requiredDecisions are subjective and prone to error
 Can also be applied to new products, even without historical dataDecisions depend on the expertise of individual people

Bear in mind, however, that these methods can have a particularly positive or negative impact on certain types of products and product groups. For example, programme-based demand forecasting is particularly suitable for specialised products, whilst consumption-based demand forecasting is particularly well-suited to mass production.

Needs assessment in practice

When carrying out a needs assessment, you should, in practice, take additional precautions and monitor developments. To this end, you can make use of other methods, which we outline briefly below.

ABC analysis for determining requirements

As a rule, warehouse capacity is limited. It is therefore not always possible to actually stock the optimum quantity of goods for all end products. This is where ABC analysis comes into play; it helps you to set priorities and determine for which goods you should optimise your demand forecasting.

Put simply, divide your products into three categories:

A-grade products: These generate particularly high turnover and are a top priority

B-grade products: These make a moderate contribution to turnover and are only of medium priority

C-products: These are items with low sales figures and are therefore given low priority

Focus on Category A products and optimise demand forecasting for them.

Target/Actual Method

The target/actual method, on the other hand, helps you to check whether current figures match the planned figures. This approach is particularly useful in rolling planning, as it enables you to control and adjust the flow of materials. For example, how much of the requirement (gross requirement) is actually available, and what is the current delivery status? You can quickly identify discrepancies in requirements planning and prevent delivery bottlenecks or production stoppages.

Examples of how to assess requirements

Now here is another real-life example that illustrates how to assess requirements.

Example: A company manufactures pyjamas. It expects to produce 100 pyjamas during the planning period.

 ExplanationQuantity of material
Basic needsThe pyjamas are the end product100 pyjamas
Secondary requirementsTo make a pair of pyjamas, you will need: 3 metres of fabric, 2 buttons, 5 metres of thread300 metres of fabric, 200 buttons, 500 metres of thread
Tertiary needsAs an aid, add 10 ml of lubricant to the sewing machine for each pair of pyjamas.1,000 ml of lubricant, 1 sewing machine
Gross requirementSecondary needs + tertiary needs300 metres of fabric, 200 buttons, 500 metres of thread, 1,000 ml of lubricant, 1 sewing machine
Net requirementGross requirements – available stock. Available stock: 100 metres of fabric, 150 buttons, 200 metres of thread, 80 ml of lubricant, 1 sewing machine200 metres of fabric, 50 buttons, 300 metres of thread, 920 ml of lubricant

In order to comply with the planning period, the business must purchase the funds to meet its net requirements.

High-performance ERP systems such as collana diva now help you to simplify your materials management and optimise your materials planning. collana diva now brings transparency to your stock levels, so that you know your primary, secondary and tertiary requirements at all times. You can use both historical data and forecasts to determine your requirements.

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Needs assessment Simplify with diva now ERP

The benefit for you? With collana diva now, you can manage demand forecasting effectively – without overstocking or understocking. Processes run smoothly and efficiently, and you can fulfil orders on time.