[lbo-talk] increasing deviations from Benford's Law

Andy andy274 at gmail.com
Sat Oct 15 09:17:04 PDT 2011


http://econerdfood.blogspot.com/2011/10/benfords-law-and-decreasing-reliability.html

<blockquote>

A second earth-shattering fact is that there are more numbers in the universe that begin with the digit 1 than 2, or 3, or 4, or 5, or 6, or 7, or 8, or 9. And more numbers that begin with 2 than 3, or 4, and so on. This relationship holds for the lengths of rivers, the populations of cities, molecular weights of chemicals, and any number of other categories. What a blow to any of us who purport to have mastered the basic facts of the world around us!

[...]

In fact, Benford's law has been used in legal cases to detect corporate fraud, because deviations from the law can indicate that a company's books have been manipulated. Naturally, I was keen to see whether it applies to the large public firms that we commonly study in finance.

I downloaded quarterly accounting data for all firms in Compustat, the most widely-used dataset in corporate finance that contains data on over 20,000 firms from SEC filings. I used a standard set of 43 variables that comprise the basic components of corporate balance sheets and income statements (revenues, expenses, assets, liabilities, etc.).

[...]

Deviations from Benford's law have increased substantially over time, such that today the empirical distribution of each digit is about 3 percentage points off from what Benford's law would predict. The deviation increased sharply between 1982-1986 before leveling off, then zoomed up again from 1998 to 2002. Notably, the deviation from Benford dropped off very slightly in 2003-2004 after the enactment of Sarbanes-Oxley accounting reform act in 2002, but this was very tiny and the deviation resumed its increase up to an all-time peak in 2009.

[...]

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-- Andy



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