English to Spanish Bus/Financial Finance (general)

"The volatility of the previous reporting period dissipated over the past month and ***credit spreads rallied*** across all asset classes. Cash spreads and CDS indices moved tighter across the board with higher beta sectors demonstrating the most significant recovery. It now appears the market has recognised most of factors behind the sharp market correction last month were unlikely to cause serious or widespread economic problems."

How would you define the meaning of "credit spreads rallied" in English? I'm not interested in its translation.

Thank you!!