By: Larry MacDonald

Many investors believe in Warren Buffett’s and Charlie Munger’s credo of buying shares in companies with durable competitive advantages. So they regularly check the quarterly 13F form filed by Berkshire Hathaway Inc. with the SEC to find out what the two investing gurus are up to.

But it can be a rather imperfect guide as I found while preparing a previous post, Buffett’s one good idea. For one thing, stocks showing up in the 13-F filing can be purchased by money managers at subsidiaries in Berkshire Hathaway, not Buffett or Munger.

For another thing, the SEC allows Berkshire to postpone disclosure of investments on the grounds that it may interfere with plans to build a position in the stock. So the 13F may not show investments recently made.

And the 13F does not report on privately arranged investments. That’s why the billions of dollars allocated in the fourth quarter to the perpetual preferred shares of Goldman Sachs and General Electric do not appear in the 13F.