Just 630 U.S. companies reported 674 accounting problems serious enough to warrant a restatement last year, a dramatic 24% decline from the number of companies with accounting problems in 2008, according to an analysis by Audit Analytics provided to USA TODAY. That's the lowest level of restatements since 2001, when the Enron accounting scandal set off a panic over the validity of corporate accounting.

The fact restatements are down is good news for investors, who can have greater faith in financial statements. "We aren't seeing the extent and magnitude of accounting problems as during the corporate scandal days," says Lynn Turner, former chief accountant for the Securities and Exchange Commission. "Those days are behind us."

The improved reliability of companies' books is evident from the fact that:

• There is steady and ongoing improvement. The number of companies with restatements and the number of restatements have declined in each of the past three years.
• Mistakes are getting caught sooner. Among the companies with restatements, errors covered a period of 476 days, or less than a year and a half. That's down 7% from 2008 and well below the 716 days, or nearly two years, of problematic numbers restated in 2006.
• Restatements are less serious. Restatements reduced companies' reported earnings by $4.6 million on average last year, down dramatically from the $7.2 million and $23.5 million hits in 2008 and 2006.

Strengthened regulations that are forcing companies and their auditors to inspect not just the numbers, but how the numbers are derived, are a big reason for the drop in restatements, says Audit Analytics' Mark Cheffers. New ways of overseeing audit firms are also making accountants more careful, he says.

Investors shouldn't assume corporate accounting shenanigans are a thing of the past. Some companies may be finding new ways to avoid restatements, although those cases are more the exception than the rule, Cheffers says.

The true test may come in the next few years when companies can no longer hide behind the economy for poor results and look for other ways to boost results, says Denton Collins, professor of accounting at Texas Tech. "The hope is we've resolved the problem," he says, "but we'll have to look at the evidence."