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HL OPERATIONS MANAGEMENT PRODUCTION PLANNING . IB BUSINESS & MANAGEMENT - A COURSE COMPANION: P275-279. Traditional Methods of Stock Control. As the debate over whether to use JIT or JIC goes on, many businesses continue to use the more traditional methods of stock control.

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hl operations management production planning



traditional methods of stock control
Traditional Methods of Stock Control
  • As the debate over whether to use JIT or JIC goes on, many businesses continue to use the more traditional methods of stock control.
  • While a lot of stock control is now computerized, there is still a need to understand the process and anyone who has worked in a warehouse will know that what it says on the computer screen may not be what they find on the shelves.
two perspectives on holding stock
Two Perspectives on Holding Stock
  • There are two sides to the question of holding stock.
  • On one hand there is cost of not having stock when required – the cost of lost orders and emergency deliveries.
  • On the other hand, there is the cost of holding too much stock – the cost of storage and damage.
diagram explanation costs of holding stock and stock out
Diagram ExplanationCosts of Holding Stock and Stock Out

Total Cost

  • By combining the two sets of costs we can see that the minimum point of the total cost is what we call the economic order quantity (EOQ) and this is the amount that should be ordered for a given time period.
  • Usually the calculations are made on an annual basis.
diagram explanation costs of holding stock and stock out1
Diagram ExplanationCosts of Holding Stock and Stock Out

Cost of Holding Stock

  • If we do not have any stock there are no costs, but then the cost rises as we store more and more units.

Cost of Stock Out

  • If we have a small amount of stock, then the cost of having a sudden surge in demand can be a huge, but this will go down the more stock we buy in.
diagram exercise economic order quantity
Diagram Exercise:Economic Order Quantity

Using the above data, create an accurate diagram to show the EOQ point.

traditional stock control diagram

Together with the EOQ, the process of controlling stock is shown by using the following terms:

The initial Order

  • The first amount of stock delivered, say at the start of the year.

Usage Pattern

  • How much stock is used over a given time period. Usually the pattern is considered to be regular or at least to have predictable highs and lows (Christmas, Chinese New Year, School holidays, etc). In general, the stock is depleted over time and so is shown by a line with a negative slope
traditional stock control diagram1

The Maximum Stock Level

  • The maximum amount of stock held at any one time.

The Minimum Stock Level

  • The amount of stock that is kept back as a reserve, sometimes called the buffer stock.
  • The amount of stock never goes lower than this level.
traditional stock control diagram2

The Reorder Level

  • When the stocks are depleted to a set level, this will be a signal to order a new amount of stock.

The Reorder Quantity

  • The amount of stock that is ordered each time.

Lead Time

  • How long the stock takes to be delivered.
traditional stock control diagram3

Explanation of Diagram

  • In the example assume it’s a company making phones for Nokia.
  • The factory staff may order an initial delivery of 1500 hand phones and they always want to keep a reserve of 600 phones just in case
  • The factory’s production manager has calculated that, barring unforeseen changes in usage patterns, he will run though 900 phones over a three month period.
  • After two months he knows that stock will run down to 900 phones and that is when he arranges for a new delivery of phones to be made from their suppliers.
  • It takes one month for that reorder quantity of 900 phones to arrive and when they do the whole cycle is continued.
traditional stock control diagram4
  • This is a simple example, but we can alter the usage patterns to take account of seasonal differences and odd surges in demand.
  • Indeed, many businesses will also have the software to do this, but the basic diagram remains.
  • It is very useful tool for production managers to see where the stress points are likely to be and how to resolve them.
traditional stock control diagram exercise
Traditional Stock Control DiagramExercise

In a 12 month period a paint shop completes the following transactions:

  • January: Orders an initial 5000 cans of paint.
  • Every 2 months, the firm reaches a reorder level of 3000 cans.
  • The minimum stock level is 500 cans.
  • There is a long lead time between ordering stock and stock arriving of up to 2 months.
  • Draw an appropriate stock control diagram based on this information.
optimal stock levels

In order for a business to calculate the optimal level of stock, there are a number of factors that need to be taken into account.

  • The Market
  • The Final Product
  • The Stock
  • The Infrastructure
  • The Finance
  • The Human Resources
optimal stock levels the market
  • Is it growing?
  • Is the business increasing sales?
  • Are there any new organizations coming in to the market?
optimal stock levels the final product
  • What type of product is it?
  • Is it cheap, single moving, fast moving, high volume product or is it the opposite?
  • Is it a complex product requiring many individual components?
optimal stock levels the nature of the stock
OPTIMAL STOCK LEVELSThe Nature of the Stock
  • Is it perishable?
  • Is it likely to be out of date?
  • Is it big – Will it take up much storage space?
optimal stock levels infrastructure
  • Is it reliable or is there a need to stockpile?
  • Will the weather have a bearing on the ability of suppliers to meet demand?
optimal stock levels the finance
  • Does the business have the required money at the right time?
  • What possibilities for credit do the suppliers allow?
  • Are there going to be significant savings from buying in bulk?
optimal stock levels the human resources
  • What are the implications for resourcing changes in stock holdings?
optimal stock levels1
  • Using the EOQ and stock control diagrams, businesses may get some idea of the correct amount of stock to order and when, but overall it is difficult to judge precisely.
  • They should be aware that many factors change and this creates more pressure depending on the system that they are using.
  • It is for this reason that the JIT system requires greater coordination and cooperation with suppliers than the JIC system which, although it may tie up lot of funds, it is safer.
capacity utilization

Production managers often want to know:

  • How efficient is the facility?
  • Is it being used to its maximum capacity?


  • A hotel might may want to know the occupancy rate of its rooms.
  • A factory may want to know how often machine

breakdown affects the work done.

  • A school principal may want to know whether there is a chance to use the school facilities more at weekends and holidays by renting the site out.
capacity utilization1
  • It is theoretically possible for a hotel to be full all year round, or a factory to work at full capacity – that is 24 hours a day, 365 days a year or in fact a school to house a day school and a night school in the same buildings.
  • However, the reality is that there will be times of the year when it is impossible to fill all the hotel rooms, and in fact the hotel may use some slack time to update or otherwise overhaul the facilities.
capacity utilization2
  • Similarly slack time will be used in factories if machines need to be “rejigged” or the site needs to be cleaned and maintenance done.
  • The same is true of cleaning and maintenance in schools.
  • In practice is often not possible to achieve 100% capacity utilization, but many businesses would still aim to get as close as possible to this figure.
formula to calculate capacity utilization
Formula to Calculate Capacity Utilization

Capacity Utilization =

Actual Production

Productive Capacity x 100

capacity utilization calculations
Capacity Utilization Calculations

Hotel Example

  • If a hotel had 100 beds and on average 80 are filled then, the capacity utilization is 80%.

Factory Example

  • A factory might be able to make 100,000 pairs of shoes in a year, but it only has orders for 40,000. It’s capacity utilization is 40%.

School Example

  • A school with sufficient space for 3000 students which has 2900 students on the register has 96.6% capacity utilization.
high capacity utilization
High Capacity Utilization
  • Businesses where profit margins are low (eg: budget airlines and fast food outlets) should aim for high capacity utilization.
  • These businesses cannot afford to lose any opportunity to sell the product and so will need to market their product accordingly.
mid to high capacity utilization
Mid to High Capacity Utilization
  • Business Class Travel or Michelin 5 Star Restaurants will not aim for 100% capacity utilization.
  • 70 to 80% may be very acceptable.
outsourcing subcontracting


  • A business can cut costs and so lower prices in order to earn a competitive advantage using outsourcing.
  • This is also know as subcontracting or contracting out work.
  • The business cuts back on its operations in order to focus on core activities.
  • Offshoring occurs when a business can outsource outside the home country.
  • With improved global communication, this has been a growth area in the modern business environment.
  • India for example, has seen a huge growth in IT offshore contracts such as call centres and help desks signed up with western businesses.
contractors may achieve economies of scale
Contractors may achieve economies of scale!
  • Traditionally a business may have had a number of activities happening on a day to day basis, many of which may not have been part of the core business skill sets, so they become transferable and thus a saving for the business.
  • Peripheral services can be contracted out.
  • Contractors which specialize in a particular peripheral service may be able to achieve economies of scale.
costs for businesses circle representation
Costs for Businesses:Circle Representation
  • Imagine that the costs of a business can be represented by circles, comprising the two different elements – core and periphery.




contracting out for a school
Contracting out for a School

A school might have as its core activity – the teaching, but it then can outsource such services as:

  • Catering
  • Transports
  • Duties and Invigilation.
  • Coaching
  • Expeditions
  • Staff Training
  • Recruitment
  • Security
  • Maintenance
  • Cleaning.

All of these could probably be provided at a lower cost and with a better result than if the school tried to complete all the tasks itself.

typical functions that are outsourced
Typical Functions that are Outsourced


  • Eg: Using an advertising agency.


  • Eg: Licensing a producer to make your product.


  • Eg: Employing an agency to “headhunt” potential staff.


  • Hiring accountants to run an external audit.
what are the advantages of outsourcing
What are the advantages of outsourcing?
  • It can reduce costs by losing employees and other assets.
  • Costs can be restructured by reducing the fixed asset element.
  • It can allow the business to focus on its core activities.
  • The quality of the product that is produced should improve.
  • It can lead to improved capacity utilization
  • Delivery time can be reduced.
  • It can lead to a transfer of expertise.
risks associated with outsourcing
Risks associated with Outsourcing
  • There will be a different corporate culture (and national) culture, but for the outsourcing to work there has to be “synergy”
  • The business becomes more dependent on the supplier (reliability, for example for deliveries can be an issue)
  • The business has less control of the final product (there may be issues of quality and ethics, eg: the use of sweatshops)
  • Communication can be difficult (especially when people are having to deal with different languages and time zones)
  • Dilution of the brand can be a problem – if the consumer realizes that product “x” is not produced by company “y”
renewed move towards insourcing
Renewed Move towards Insourcing
  • There are many reasons why businesses still prefer to produce at source rather than by outsourcing and especially by offshoring.
  • In fact, there is also a new idea beginning to gain ground in the business environment - insourcing – that is reversing the trend by taking back jobs lost to offshoring overseas by focusing on the quality end of the market.
  • Particularly with service-based products, there is a lot to be said for local knowledge.
make or buy decisions
Make or Buy Decisions
  • Very often the decision about whether to outsource or not hinges on costs.
  • The issue is whether it is cheaper for a business to buy a product made elsewhere OR to make it themselves.
  • The decision can be shown very clearly by using the costs and revenue formulae in this section
ctb ctm equations
CTB & CTM Equations

Cost to Buy (CTB)

P x Q

Cost to Make (CTM)

FC + (VC x Q)

school example lease buses
School Example: Lease Buses
  • A school has to decide whether to subcontract the bussing in of students or to provide the service themselves.
  • What is the school requires 20 buses and a company called School Run charges $10,000 a bus for the year? Then according to the formula the service would cost the school:

(P) 20 x $10,000 = $200,000

school example buy buses
School Example: Buy Buses
  • If the school could buy 20 buses from Dodgy Dealers Inc for $100,000 but faced variable costs of $10,000 a bus for fuel and the drivers wage over the year, then the cost to make the service using the equation

CTM = FC + (VC x Q)

$100,000 + ($10,000 x 20) = $300,000.

In this case CTB < CTM so the school should outsource.

school example other factors to consider
School ExampleOther Factors to Consider
  • The previous example ignores many of the factors that may have a bearing on the supply chain. Key Questions might be:
  • How reliable are the buses bought from Dodgy Dealers?
  • What are the implications of the school employing drivers as opposed to someone else doing so?
  • When deciding on what action to take, a business would take qualitative factors such as these into account.
ctb ctm calculations
CTB & CTM Calculations

An airline must decide whether or not to run its own catering division or sub-contract out this responsibility to a third party for a 5 year contract. The following information is available.

  • The Quality Airport Catering Company will charge the airline $5 for each meal produced - 15 million meals are required per year by the airline.
  • The catering company will increase its meal costs by 5% each year over 5 years.
  • If the airline were to produce its own meals, it would be faced with fixed costs of $5,000,000 to buy an initial facility/building and to buy relevant equipment (eg: stoves-ovens). It would then face a wage bill of $500,000 per year and another $200,000 in operating expenses (eg: electricity) The cost of buying food ingredients would be $2 per meal.
  • What should the airline do? Use CTB and CTM equations to justify your decision. Should the airline outsource its catering??
ctm for the airline
CTM for the Airline

1 million



1.7 million is fixed costs per year

VC 15 m x 2 = 30 million

30 + 1.7 x 5 = $158 million


Year 1 - 15 x 5 = 75

Year 2 75 x .05 = 3.75 = 78.75

Year 3 78.5 x .05 = 3.925 = 82.68

Year 4 82.68 x .05 = 4.134 = 86.814

Year 5 86.814 x .05 = 4.340 = 91.2