Gross Margin Return on Inventory Investment A Tool for Our Times

Since last fall, as our new economic reality has evolved, I’ve had a few things to say about what to do. They’ve included building your balance sheet, controlling your inventory and other expenses, focusing on the gross profit line, looking at gross margin dollars as well as percentages, and making good use of your management accounting system, which I consider a strategic tool in this environment.

All very sage and business like stuff I’m sure you’ll agree. Trouble is, I didn’t really have a method to help you do it all. Problem solved.
Serendipitously, Cary Allington, President of ActionWatch, the collector and supplier of sophisticated, detailed retail information on what’s selling at what prices and margins in our industry sent me an article on the Gross Margin Return on Inventory Investment concept (GMROII). He was pretty excited. So was I after I’d read it.
The concept isn’t new. It’s valid for brands and retailers. It comes as close as I could hope to drawing together most of the ideas I’ve been talking about lately. Hopefully, you’ll read this and say, “Oh hell, I already know and do all that.” But I don’t think so. Neither does Cary, who spends a lot of time talking with retailers and brands about the data they have or want and its quality.
What Is It?
GMROII is a conceptually simple method for measuring which inventory items (or categories, or brands) give you your best return on your investment in that inventory. It combines gross profit with inventory turns in a way that allows you to compare the profitability of snowboards (or a particular snowboard) with, say, surf wax at the gross profit level. It’s not perfect, and we’ll discuss the caveats below, but it looks like it can be very useful.
Just as a refresher, inventory turn refers to how many times you have to replenish your inventory for a given level of sales over the year. It’s important because the more turns you have, the less inventory you can carry for a given level of sales. And the less chance your inventory will have to be marked down. Carrying extra inventory costs you money in lots of ways including cost of capital, overhead, and opportunity cost when you have money tied up in something that takes a long time to sell and has to be discounted instead of in fast moving, full margin inventory. 
The GMROII calculation itself is simple. It’s just the number of gross margin dollars you make selling a product (or category or brand) over whatever period of time you choose to measure it divided by the average inventory at cost over the same period. Typically, it’s done over a year. The result is a number (in dollars- not a percentage) that tells you how many gross margin dollars you earned for each dollar invested in inventory over the period.
Having calculated these numbers, what might you do with them? For the first time, you’ll be able to compare what I’ll call the inventory financial efficiency (I just made that up! Kind of like it) of any item you sell with any other item. You can also do it for a brand or a category. You can actually say, based on the example above, I’d rather sell the same amount of Item A than Item B even though one sells for $600 and the other sells for $12.00 and they are in completely unrelated categories. You can see which ones you’re wasting your time selling (or at least recognize that there’s no financial reason to be selling them). You can eliminate too much emphasis on gross profit margin, which I think you can see in the table below can be misleading. You may significantly reduce your inventory investment.
Below is a table supplied by ActionWatch that calculates the GMROII for a number of categories using data they collected from their panel of retail shops.



The GMROII is the number of gross margin dollars generated for each dollar of inventory you had in that category over the period of a year. If you could plan your whole business around GMROII, obviously you’d get rid of everything but long completes and just sell them. But your customers probably wouldn’t go along with that.

That shoes are at the bottom of the list isn’t a surprise, at least to me. Given all the color, sizes, and styles you have to carry the inventory investment is pretty significant. The opportunity is to calculate the GMROII for each SKU and figure out how you can change your mix to drive that shoe GMROII up.
I was kind of surprised to see the GMROII for accessories as far down on the list as it was. We’re all favorably disposed to accessories and think of them as a high margin, profitable product. This particular analysis suggests they aren’t quite as spiffy as we thought.
That skate hard goods all had GMROIIs higher than soft goods was kind of a surprise. I’d especially note the high values for short decks. We bitch and moan that the gross margins need to be higher, but because of the speed at which short deck inventory turns, they look pretty good in a GMROII analysis. This analysis doesn’t break out branded from shop decks. That would be interesting to see.
Notice how increasing the annual inventory turns boosts the GMROII even when the gross margin percentages are lower. You’d rather have an extra half turn on that inventory than a couple of gross margin points any day. But how many of you calculate the inventory you buy based on the dollars you have to spend and the percentage gross margin you expect to make? You can’t ignore those factors, but pretty clearly turn needs to be part of the analysis. 
The basic calculation for GMROII is conceptually simple as you can see. But I’m afraid it requires some work. What an inconvenience.
The System Thing
You won’t be doing a lot with GMROII unless you have a quality management information system. For the calculations to be meaningful, your sales history and inventory tracking have to be solid. If you want to track it by category or brand, your chart of accounts has to have been set up to aggregate the numbers. And of course this isn’t a onetime activity. You need to keep it current as product comes and goes, as credits are processed, as write downs occur. You get the picture.
I’ve talked about the need for good systems before. I’ve gone so far as to say you can’t get by without one- especially now. Some systems do the GMROII calculations for you. I’ve been told that these include Cam Commerce, which offers it in their Retail STAR and Retail ICE applications. Win Retail also offers it. I’m not sure which systems for brands might offer it.
Other Considerations
You can’t just keep the products with the highest GMROII. Total dollars generated matter and there are other reasons besides financial to stock a product. You can have products with huge GMROII that wouldn’t generate enough gross margin dollars to cover expenses (and some bottom line profit besides would be nice).
You have to already have been carrying a product for a period of time before you can do the calculation. If you want to conduct a GMROII analysis at the item level, it works best for items that you replenish rather than replace. If you’re out of inventory for a period of time, that will impact the value of the calculation.   In general, the longer you’ve carried the product, the better the calculation will be because the average inventory number will be more accurate. 
Come to think of it, for those of you who are statistically inclined, I recommend calculating the mean inventory and the standard deviation (dispersion around the mean) rather than just average inventory. That would give you a good sense of whether or not you can calculate GMROII for shorter time periods. Though I suppose you’d need to calculate it for the same period for all products to get comparable results.
If only because it gives a result in dollars, GMROII is not a traditional return on investment calculation and should not be confused with one. It’s a way to manage your inventory- not your whole business. But inventory is often the biggest number on your balance sheet, so managing it well pays big dividends. How might you start?
To take the greatest advantage of the concept, you really do need the good system and data I describe above. Just to work up some enthusiasm, assuming your system isn’t quite set up to make the calculations, get a pencil, calculator, paper and inventory and sales records going back a year. Pick, oh, I don’t know, sunglasses. Choose a brand. Or a style or color. Whatever it’s easy to get the data for.
Figure out the total gross margin dollars (after all allowances and markdowns) you earned on that product or product group over the year. Now add up the inventory at cost of the product or product group at the end of each month over the last year and divide by 12. Divide the gross margin dollars by that average inventory number and you’ve got your GMROII.
Next, depending on what you decided to do the first calculation on, do it again for another brand, color, or style. Now you’ve got the GMROII for two groups of products. Is the result similar? If not, why not? Was a style you ordered the most of just a dog? One brand just cooler than the other? Did the order get screwed up?
What adjustments should you make in your purchasing so you’re selling more of the higher GMROII stuff?
Now, for even more fun, do the same calculation for surf wax. Or whatever. Which should you want to be selling more of; the sunglasses or the surf wax? Bet you didn’t have a way to figure that out before.
It won’t be as simple or clear cut as I’m making it sound here. It will never be exactly accurate, but the more you use it, the more useful it will become. It’s clearly harder to do with seasonal merchandise and changing styles, but I think it’s worth the extra work, though the quality of your information won’t be as good.
Cary has put a link to the article I referred to on the ActionWatch web site. You can access it in the section called “POS Tips Links” at   The GMROII concept is worth some of your time. There’s a bunch of money on the table.