Thinking about inventory in terms of time is the essential starting point in
effectively managing inventory. Stated in simple terms, the goal of effective
inventory management is to have on hand at any given time only enough inventory
to support planned sales until the next delivery arrives, plus a safety stock to
cover any short term sales spike and the possibility of a late vendor delivery.
This quantity can be stated at any point in time as forward weeks of supply;
that is, the number of weeks of planned sales going forward that the current
inventory represents. When thinking in terms of weeks of supply the focus is on
maximizing the return on the inventory investment by linking inventory levels
directly to planned sales.
However, many small retailers instinctively focus on how much they might be
able to sell if they had the stock on hand, rather than the amount of cash they
are committing to inventory. Their focus is on having the stock to be able to
capture the ‘last sale’. The problem with trying to capture that ‘last sale’,
however, is that it’s not possible to know exactly which sale is the ‘last
sale’, resulting in inflated inventory levels. And unless they can quantify the
number of weeks of supply they have on hand, and the number of additional weeks
of supply they are purchasing, they have no way of projecting when they can
expect to sell that inventory and convert it into cash.
Clearly, a critical component of forward weeks of supply is planned sales.
For small retailers of non-seasonal items, these sales plans can be arrived at
quickly by taking the current weekly rate of sale and applying a factor for the
current sales trend. For seasonal items, a quick sales plan can be developed by
taking the prior years sales for the same period and applying the sales trend
factor. For larger retailers, more elaborate demand forecasting software
applications are frequently utilized. The point of this discussion is not to
review various forecasting methods, but to emphasize the importance of a well
thought out sales plan arrived at through careful analysis of past sales volume
and patterns, and current trends.
To become a truly powerful inventory management tool forward weeks of supply
needs to be calculated continually by category or item. For categories of
fashion merchandise, for instance, where specific items are constantly changing
as assortments, forward weeks of supply should be calculated by category. For
staple replenishment items, forward weeks of supply should be calculated by
item. And just as on hand inventories should be thought of in terms of forward
weeks of supply, purchase quantities should also be evaluated for the number of
additional weeks of supply that they represent. Every purchase order should be
accompanied by the following question; “How many weeks am I buying?”
Finally, after I’ve taken a moment to explain the concept of weeks of supply
to a prospective client, they invariably ask what the weeks of supply should be
for their business. And just like they started the conversation by not knowing
what their weeks of supply was, I end it by not being able to tell them what
their weeks of supply should be. Every retailer has a different optimal weeks of
supply, due to their unique mix of product offerings, which have unique selling
characteristics, customer expectations and supply chains. And for most
retailers, especially those whose product offerings are highly seasonal, the
optimal weeks of supply may vary significantly throughout the year.
The point is not necessarily to identify what the optimal weeks of supply is,
but to continually challenge the current forward weeks of supply to identify
opportunities for eliminating unnecessary inventory, and free up cash for other
urgent needs. For as every retailer understands, there’s no such thing as
standing still; if you’re not going forward, you can be almost certain that
you’re going backwards.
Small retailers who think of their inventory in terms of weeks of supply
almost always experience fewer markdowns and fewer build-ups of dead inventory,
faster inventory turnover, and healthier cash flows. With healthier cash flows,
and a keen eye on weeks of supply, a small retailer will always have the ability
to be a true merchant, to make that advantageous purchase, chase a key item or
capitalize on the latest emerging trend. And those are the true keys to
generating consistent sales increase and profitability.
© Ted Hurlbut 2004
Ted Hurlbut is the Principal of Hurlbut & Associates,
which helps retailers, wholesalers, importers and distributors improve the
productivity of their inventory investment. Please visit
www.hurlbutassociates.com for more information.
