What is a WSSI and why is it important?

The WSSI is an industry standard tool which supports the decision making of Retail Buying, Planning and Trading teams. First Friday have been involved with many WSSI projects and offer some thoughts on why any retailer who needs to manage the risky business of buying stock ahead of the season needs a WSSI to help them.

You may not have a WSSI, and, having survived without, you may wonder what the fuss is about. Or you may be wondering why you are under pressure from your team to replace the old Excel WSSI which has been around for years. What is this WSSI, why is it so important, and why are we at First Friday passionate about it?

What is a WSSI?

WSSI stands for Weekly Sales, Stock and Intake. A WSSI shows past, present and future performance by week. It can be used both to create a plan, and then in the trading period to review and react to performance against that plan. It is not a report – even if it is viewed on paper – but a decision-making tool, supporting the process by which Sales, Stock and Intake are managed to maximise profit and minimise risk. Open to Buy is generated to ensure that the right stock is available at the right time, while terminal stock targets allow for the management of seasonal stock down to an appropriate level.

It is important to remember that the WSSI is not the process itself, and that if the process is broken, the existence of a WSSI will not fix it.

Why is a WSSI important?

Let’s put the question another way; how are you operating without a WSSI?

  • Do you have a mechanism for revising your original plan in the trading period to create a forward forecast which reflects performance?
  • Can you see past performance and future projections alongside each other?
  • Can you be sure that your forward forecast potentialises the trends emerging through current performance rather than holding you to a plan which may now look outdated?
  • Can you see at a glance that you will have enough stock to potentialise demand in future months – without incurring the risk of holding excess stock?
  •  Do you have a mechanism to calculate how much additional stock should be bought to meet ideal stock levels?
  • Are you able to manage sales, stock and intake by season to avoid excess terminal stock of unsaleable seasonal product – without excessive clearance markdown spend?
  • At what levels of the product hierarchy can you see this?
  • Can you forecast bottom up, or are you always looking at the top down view? Can you roll up bottom up views to give a top down view?
  • Can you be sure that you are potentialising individual sales channels rather than simply looking at the sum of the parts?

And if the answer is “yes thank you” to all these questions, we have a few more for you:

  • How much effort are your teams having to put in to give you this information?
  • How much more time is being spent providing information to impacted functions like Finance and the DC to inform their decision making?
  • Have you unwittingly created a cottage industry of Excel spread sheets which pull information from myriad systems to give you what you want – whilst leaving your teams little time to do what you are paying them to do?

At First Friday we are passionate about the WSSI, and our clients confirm its importance to them. The first thing they notice is the ease of decision making when all the data is in one place. Visibility of past, present and future sales, stock and intake facilitates decisions:

  • How much more stock is needed to meet the anticipated level of sales?
  • What events might be needed to boost sales?
  • How much stock needs to be phased back to react to sales at lower than planned levels?

The WSSI acts as a dynamic plan, enabling teams to re-forecast within the trading period rather than holding to the stock levels they originally planned. Rolling up Department or Channel WSSIs gives a Company view, whilst working bottom up from levels below Department helps to potentialise growth areas and minimise risk in those which are underperforming. Automated data feeds from sales, stock and commitment systems release users from mundane data inputting and free up thinking time to make decisions with the data.

Nor are the benefits of the WSSI confined to the Buying, Planning and Trading teams. The WSSI will also provide:

  • Visibility of forward sales and intake supports cash flow forecasts in Finance
  • Intake and despatch forecasts aid flow planning through the D.C.

In short, we believe the WSSI is critical for the effective management of sales, stock and intake, and the avoidance of high markdown costs when things don’t go to plan.

This then is why the WSSI is so important.

What do you need to consider next?

Whether you decide to introduce a WSSI for the first time, or to upgrade your current solution, the possibilities of the WSSI are endless.

There are many things that you will need to consider:

  • Assess what is desirable in your business
  • Assess what is possible in your business with the data that you have
  • Review your processes and identify any opportunities for improvement
  • Clarify your requirements for a system
  • Undertake selection of the best fit software
  • Plan how best to manage the change within the business
  • Plan how you will train your teams to work with the new tools and / or process.

To help you get started, look out for our next article:

“Considerations when choosing and implementing a WSSI”.


Do you need to upskill or train your team in merchandising?

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  • Choose just the modules you need, or go all-in
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The courses that cover the use of a WSSI are


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Kathryn Fletcher

About the author: Kathryn Fletcher

Kathryn: A Principal Consultant at First Friday since June 2002, with over 30 years’ experience in retail from major supermarkets to High Street fashion chains to department stores. Kathryn’s specialties are in Buying, Merchandising, Planning and Trading, software selection, systems implementations, capability improvements and training. Fun Fact: Kathryn is a founding trustee for Future Pillars, a charity empowering vulnerable children in Zambia.

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