The article analyzes what causes changes in credit default swap spreads for US companies before and during the financial crisis. By looking at different factors like leverage and volatility, the researchers found that these factors can explain over half of the changes in CDS spreads. They also discovered that since the crisis began, CDS spreads are more affected by leverage and less by volatility. Additionally, a common factor has been driving CDS spread changes during the crisis, which is not related to economic indicators or risk factors.