three sets of books

A couple of years ago, I wrote a post about the three sets of accounts that a publicly traded company maintains:

–tax books, where the objective is to pay the smallest amount of tax legally possible–in other words, to fool the IRS,

–financial reporting books, where a more liberal view of when and how revenues and expense occur allow a company to put its best foot forward with owners–in other words, to fool shareholders, and

–management control books, also called cost accounting books, which the company uses to actually run its operations.

contribution margin

Contribution margin is a cost accounting concept.

The first thing to note is that despite its name it’s not really a margin–that is, it’s not a percentage.

Instead, it’s the amount by which an activity or a  line of business exceeds its own direct costs and makes a contribution to corporate overhead.  This isn’t the same as making a standalone profit, meaning after covering total costs.

Take a restaurant that’s now open for lunch and dinner and makes money doing so.

Should it open for breakfast, as well?

In the simplest case, the question is whether the restaurant can generate enough revenue to offset the cost of paying for the food and the staff.  If so, it makes a positive contribution margin.  If we were to allocate, say, 20% of the restaurant’s total expense for rent, electricity and depreciation of equipment,  breakfast might be bleeding red ink.  But those costs are there anyway, whether breakfast is or not.  As long as the contribution margin is positive, the firm is better off with breakfast than without.  (Yes, the actual situation is more complicated   …is the wear and tear higher because of breakfast?   …does breakfast cannibalize the other meals?   But I’m keeping it simple to illustrate a point.)

Another case.   Some lines of business may never have been intended to create growing profits, or may no longer be capable of doing so, even if they once were.  A manufacturer may make precision components in-house.  The component division will typically be run as a cost center, not a profit center.  It’s mission will be to provide high quality parts at the lowest price, not to maximize profits.  Its managers will be evaluated by their ability to provide output more cheaply than third-party alternatives can.  Again, the division may not be profitable after allocation of its share of corporate overhead.  Still, it may be very valuable.  Its value will be measured by contribution margin, defined as the difference between in-house and third-party component costs.

Why is this important?

It’s a mindset thing.  Not every part of a company may be intended to grow.  Rising stars may eventually turn into cash cows as businesses evolve.  It’s important both for company management and investors to understand the role an activity should be playing in the overall enterprise.