The study looked at whether bond ratings give important information to investors that they can't get elsewhere. They focused on how investors reacted when Moody's changed its rating system without any big changes in the risks of the bonds. The researchers found that before Moody's made the new ratings public, bond prices didn't match the new information Moody's had. After Moody's announced the new ratings, bond prices changed to reflect the new information. The stock prices of the companies that issued the bonds also changed, but in the opposite direction. Overall, the total value of the companies wasn't significantly affected by the new ratings. This suggests that the information in rating changes about the risk of default can be spread out across different investments.