The effect is robust over time, economically significant, unlikely to be caused by data-mining, and not related to taking excess risk.

FORBES: Selling In May Is Very Good Advice This Year

The effect is robust over time, economically significant, unlikely to be caused by data-mining, and is not related to taking excessive risk.

FORBES: Time Of The Season To Be Bullish

Asked whether new laws were needed to enforce mining codes, Golborne said the laws were not to blame for the men's predicament: "The problem was that the owners did not do what they were told to, " he said.

CNN: STORY HIGHLIGHTS