The board began work in 2003, and fairly quickly found problems. In the first year of reviews, it noticed that one company had overstated its current assets, making it look better. It then checked other companies and found that the error was widespread, involving customers of each of the Big Four. A round of restatements followed.

The 2010 reports — the most recent available and the ones with the high level of deficient audits — concerned audits of 2009 financial statements. Inspectors focused on financial companies, and zeroed in on the willingness of auditors to accept valuations of complex securities without determining whether the valuation methods used were reasonable.

That year, 2009, was also the year that politicians put heavy pressure on the Financial Accounting Standards Board, which sets accounting rules, to relax rules on marking securities to market value. At a public hearing in March, Robert H. Herz, then the chairman of the standards board, was excoriated by members of the House of Representatives capital markets subcommittee for issuing rules that made the banks look worse than they deserved to look. FASB (pronounced FASS-bee) soon relaxed the rules, and auditors were expected to assure compliance with those newly eased rules.

Some accountants privately speculate that some of the lapses found by oversight board auditors could have been influenced by the pressure not to make banks, already in trouble, look worse than was necessary.

In its inspections of the audits of 23 brokerage firms, many of the auditing lapses found by the board dealt with the failure of the auditing firms to do enough work, at least in the inspector’s view, to justify a conclusion that the numbers were correct. In 15 of the 23 audits cited in this week’s report, “firms did not perform sufficient procedures to test the occurrence, accuracy and completeness of revenue.” In six of the nine audits where the auditor had to deal with how much securities were worth, “firms did not perform sufficient procedures to test the valuation.”

That is different from saying that the auditor reached the wrong conclusion.

In the 2010 inspection of PricewaterhouseCoopers, auditors were found to have missed significant errors in how one company accounted for derivative securities it owned. The board inspectors cited no other errors in financial statements, but in 27 of the PWC audits — out of 71 reviewed — the auditors failed to perform work that the board thought should have been done.