Munger on Accounting

In a now-famous talk given to a group of students at USC Business School in 1994, legendary investor, Charles Munger, described a number of mental models. One of the mental models accounting and double-entry bookkeeping:

"One of the advantages of a fellow like Buffett, whom I've worked with all these years, is that he automatically thinks in terms of decision trees and the elementary math of permutations and combinations.... 

Obviously, you have to know accounting. It's the language of practical business life. It was a very useful thing to deliver to civilization. I've heard it came to civilization through Venice which of course was once the great commercial power in the Mediterranean. However, double-entry bookkeeping was a hell of an invention.
And it's not that hard to understand. 

But you have to know enough about it to understand its limitations—because although accounting is the starting place, it's only a crude approximation. And it's not very hard to understand its limitations. For example, everyone can see that you have to more or less just guess at the useful life of a jet airplane or anything like that. Just because you express the depreciation rate in neat numbers doesn't make it anything you really know. 

In terms of the limitations of accounting, one of my favorite stories involves a very great businessman named Carl Braun who created the CF Braun Engineering Company. It designed and built oil refineries—which is very hard to do. And Braun would get them to come in on time and not blow up and have efficiencies and so forth. This is a major art.
And Braun, being the thorough Teutonic type that he was, had a number of quirks. And one of them was that he took a look at standard accounting and the way it was applied to building oil refineries and he said, "This is asinine." 

So he threw all of his accountants out and he took his engineers and said, "Now, we'll devise our own system of accounting to handle this process." And in due time, accounting adopted a lot of Carl Braun's notions. So he was a formidably willful and talented man who demonstrated both the importance of accounting and the importance of knowing its limitations."