There has been a dramatic increase in restatements over the last few years. It's been estimated that the number made in 2006 was three times the amount from 2003. But what's driving the increase? Is it because of increased complexity? Or is there something more basic?

A new study, An Analysis of the Underlying Causes of Restatements, found that restatements of companies were usually the result of internal mistakes made by their own accountants and the failure of their auditors to catch them.

The research, conducted by Marlene Plumlee of the University of Utah and Teri Lombardi Yohn of Indiana University raised doubts about claims that they were the result of the complexity of accounting standards enacted in the wake of financial scandals earlier this decade.

"Our results document that restatements are primarily caused by basic internal company errors unrelated to the accounting standards," they write. "However, those restatements caused by some characteristic of the accounting standards are most often attributed to the lack of clarity in applying the standards and/or the proliferation of the literature due to the lack of clarity in the original standard."

The study is significant in light of claims by the critics of Sarbanes-Oxley that SOX-driven accounting complexity is driving the restatements. Instead, the study points to more basic forces at work.

Which raises a key point: no law can protect investors from stupidity.