Ambac Financial Group, Inc.'s largest subsidiary, Ambac Assurance Corporation, is in active run off and has not written new business since 2007. We are an event driven company which impacts our ability to drive our strategic initiatives. Our primary focus is on risk reduction, loss mitigation and asset recoveries with risk management playing a key role in our operations.
Ambac's Risk Management Group is primarily responsible for the development, implementation and oversight of loss mitigation strategies, surveillance and remediation of our insured portfolio. We continue to aggressively pursue and execute on various strategies to stabilize our insurance platform in order to reduce and mitigate potential adverse development, preserving future optionality and opportunities. Strategies implemented include commutations, risk transfers through reinsurance and other measures, proactive facilitation of refinancings, and policy terminations. In 2020, our active de-risking efforts resulted in an 8% decrease of our riskiest exposures, or Adversely Classified and Watchlist Credits, to $13.2 billion at December 31, 2020. By de-risking our legacy insurance platform, we believe the performance of this portion of our business will become more stable and predictable over time.
As we look to expand our operations by exploring opportunities involving the acquisition and/or development of new businesses, risk versus reward remains at the forefront of our decision-making process, including Sustainability and Corporate Responsibility.