(Reuters) - When South Korean automaker Hyundai Motor Co (005380.KS) announced last month it had overstated the fuel efficiency levels on around one million of its cars in the United States and Canada some investors were left fuming more than others.
Some had already sold their shares before the announcement on November 2. The stock fell 4 percent on November 1 with about 2.2 million shares changing hands, the highest trading volume of the year at that point.
"This smells pretty bad," said Robert Boxwell, director of consulting firm Opera Advisors in Kuala Lumpur who has studied insider dealing patterns.
"It would have fallen into our suspect trading category," he added.
Boxwell spots suspect trading by looking at how much the volume diverges from the average level in the days before a market moving announcement. In the Hyundai instance, the volume was more than five standard deviations, a measure of variation, away from the daily average of 598,741 shares over the past year.
A Hyundai spokeswoman declined to comment.http://www.reuters.com/article/2012/...8BK07M20121221