Supply Chain Planning Blog

Run Your Supply Chain without a Bullwhip!

Posted by Cyrus Hadavi on Thu, Feb 26, 2015
bullwhip

Bullwhip or Forrester effect is result of uncertainty and changes in demand that magnify as we move upstream in the supply chain. The farther upstream the supplier is, in the supply chain, the more variations in inventory levels.  Unfortunately this behavior is taken for granted for most industries. Some advocates of Kanban and JIT believe that using these techniques would eliminate such behavior and makes the supply chain more predictable to the extent that large variations are avoided. This is not a true assumption for the following reason. Kanban and JIT are not planning tools, they are execution methods. Hence they cannot be used to dynamically plan ahead of time when there are inevitable variations in demand. When you design your supply chains with a certain demand in mind, then as the demand goes down, Kanban would react accordingly unless your buffers are too large such that much of the inventory will remain unused between stages resulting in excess inventory. If the buffers are NOT big enough to avoid the excess inventory problem, then it is likely that shortages will occur when there is a surge in demand? The buffers are all used up and the pipeline will sit empty resulting in shortages and loss in revenue etc.

Here are some observations and reasons why we no longer have to run our supply chain under the assumption of bullwhip phenomena. We all know that plans are not perfect however re-planning is the key and doing it fast and in parallel is the reason why we can avoid BW effect. This is explained in more detail below. 

From Serial to Parallel

Bullwhip happens because of the serial behavior of the supply chains. In other words each downstream stage tells the stage before it until it gets to the first stage. This delay is one of the reasons for the rise in the amplitude of the inventory. However this behavior can be changed by providing multiple levels of visibility upstream using collaboration tools. Such tools can be set up to send signals to suppliers as far back as needed in order to share with them the trends in demand that are observed in the consumer behavior. Using point of sale information as well as demand signaling and demand planning technologies, the information shared can save suppliers much cost as well as make them a better and more reliable supplier.

Whole vs Segments

Another notion related to parallel analysis of the supply chain has to do with how the buffers are set up at various stages of the supply chain. In contrast to the traditional techniques of each stage deciding on their own inventory levels before, during and after that stage, Multi Echelon Inventory Optimization (MEIO) technology looks at the entire supply chain and each layer thereof in parallel, not in an isolated and serial manner. Using probability and queuing theory it can make fairly accurate predictions as to how much inventory of each item should be at every stage of the supply chain to avoid shortages and/or excesses yielding unprecedented delivery performance while minimizing cost. Such a parallel treatment of the supply chain would eliminate the BW effect and change it to a “stick effect.” MEIO takes into account both the cost and service levels at every stage given the lead-times and interactions between stages to produce a holistic solution not an isolated serial solution. 

Responsive vs Predictive

The more responsive we are the less predictive we need to be. Widespread use of cell phones have made all of us a lot more responsive. As a result we do a lot less planning. How many times have you heard someone saying “I will call you when I get there.”  In the past you had to specify exact time and location to meet up with someone! Today’s S&OP technology allows real-time planning to be more responsive. In other words within hours a new plan can be generated if and when there is a change in demand or supply. Obviously faster planning does not eliminate the time it take to physically build and transfer goods, however it does significantly shorten the cycle time to delivery. Hence it can reduce the potential amount of inventory quite considerably resulting in a more stable supply chain rather than a BW supply chain. This is more of a responsive planning in contrast to predictive planning. 

Risk Factor

The value of an item at the most downstream point in the supply chain is several times higher than the cost of an item at the most upstream location! So if you look at the weighted variation of inventory taking into account cost factors, then the variation in value is fairly constant and not as variable as the quantity depicted in the BW. This is a key issue in balancing the supply chain and risk management. In order to ensure the availability of parts, the upstream locations can take higher risks than the downstream locations. However, the way the supply chains are set up today, the reward/risk ratio is a lot higher for the downstream companies than the upstream suppliers. By making this ratio more equitable, much better and more efficient supply chains can result in terms of adaptability and responsiveness. One way to do this is a commitment to buy a minimum amount within a defined window of time. With this level of confidence, suppliers can assess their own risk and not only ensure delivery of what is needed but take additional risk knowing that they have some level of downside protection.

Although BW effect may not be completely eliminated however the size of the waves can be significantly reduced resulting in a much more stable and predictable supply chain.

Topics: Multi Echelon Inventory Optimization, Supply Chain, Supply Chain Planning, Supply Chain Performance Management, MEIO, Inventory Management Software, Inventory Management, Sales & Operations Planning, S&OP

Inventory Planning | What Does It Mean To Optimize Inventory?

Posted by Bill Green on Thu, Apr 22, 2010

Inventory Optimization

Many companies say that they want to Optimize Inventory, but they often have different things in mind when they say it. 

 

Of course, they are all looking to make better use of the inventory on-hand, and they all have the goal of keeping customer service high and inventory low.  However, what makes them different is that each company may have a dissimilar root cause as to why they are not doing better with it.

 Inventory Planning

There are four main areas of supply chain planning to focus on when trying to get more from your inventory investment.  From top to bottom, and with different time-horizons, each one is critical to get the whole picture right, so it’s important to target them individually:

 

1) Reduce forecast error with better Demand Planning

2) Establish better inventory target levels with Multi-Echelon Inventory Optimization (MEIO)

3) Further synchronize supply flow with better Sales & Operations Planning

4) Improve daily Inventory Management

 

Reducing Forecast Error

The two key factors that will impact the amount of inventory that is required in a supply chain are lead-times and demand uncertainty.  Although, forecasts will always be wrong, there is a great deal that can be done to increase their accuracy with improvements in process and technology.  Remember, you have to do everything possible to be less wrong.  Forecasts and “consensus demand” (i.e. aggregation and agreement on one forecast number, by all departments) are also used to determine forecast error.  So, if a company does not have a strong process in place to facilitate collaboration, they will not be able to do well in any of the other areas. 

 

Demand Planning is a critical component of inventory management.  We have a new ePaper on this topic entitled: Planning Demand for Profit Driven Supply Chains.  Feel free to download it by clicking on the title.

 

Multi Echelon Inventory Optimization

The amount of inventory buffering should increase along with the value of a product, the amount of uncertainty in demand relative to the sales volume, and a company’s response time to deal with supply chain surprises. 

 

Where to place inventory can be very difficult to figure out in an end-to-end supply chain with many products.  There are many ways to rebalance how inventory budgets are allocated, inventory pooling and production postponement strategies can be complex and hard to execute, as planned.  A Multi-echelon Inventory Optimization (MEIO) system will enable a company to consider all of these in deciding where in the supply chain and how much inventory to have.  If your company is using a manual system, and pretty much guessing at how many days of coverage to have for each product, or does not have a good process in place to calculate statistical safety stock values and its “What-if” impact on customer service, then you should be looking into how an MEIO system can help your supply chain. 

 

If you would like more information on Inventory Managment and its "Optimization", I recommend reading this paper: Demystifying MEIO.

 

Sales and Operations Planning

As part of the S&OP process a company needs to determine how to meet the inventory demand that comes from buffer stocks, forecasted demand, and backlog.  Or it may be that capacity or material constraints, or other operating efficiency concerns, drive a company to purchase or build inventory ahead of when it’s actually needed.  Regardless, the supply planning process that feeds a consensus S&OP plan is the place that these decisions are made.  If a company does not have a good S&OP process in place, then it will not be able to make good decisions around inventory.  Furthermore, if the S&OP system in place does not consider the effects of finite capacity, materials, and operating constraints, then control over inventory levels will not be achieved.

For more information about S&OP process, I suggest viewing this recorded webcast: S&OP 101: For all manufacturing executives

 

Inventory Management

Even with a perfect plan, a company cannot keep inventory low and customer service high unless they can execute on moving inventory through the supply chain to meet customer orders.  Better Inventory Management will give improved visibility of inventory through the supply chain and create the orders to move the inventory when required.  Inventory Management gets the target levels from the MEIO system, and then executes as orders and forecasts are received.  If a company does not have good visibility into inventory, forecasts, and orders then an improved Inventory Management system will surely help. 

 

A last thought, there are many areas of supply chain planning that can have an impact on reducing inventory and improving customer service.  Typically a company will focus on Demand Planning first, and then Inventory Management, while putting in place simple ways to set inventory target levels.  They would then focus on better inventory targets with MEIO systems and better supply side S&OP planning.  Each company is different, and it is important to address each area based on your needs.

 

About the Author:  Bill Green is the Vice President of Solutions at Adexa, for more information about him please visit his profile link.     

 

For more information about different types of Supply Chain Planning systems visit: Demand Planning, Inventory Planning, or Sales and Operations Planning.

 

Topics: Multi Echelon Inventory Optimization, Supply Chain Planning, Inventory Planning, Inventory Management, Inventory Optimization