The article explores how insurance markets can be more efficient by using continuously open markets for better asset allocation. It looks at different types of insurance contracts needed for market efficiency, considering factors like preferences and endowments. The study also examines how risks are classified based on actuarial properties and extends insurability to include correlated and catastrophic events. The researchers found that under certain conditions, a small number of standard insurance contracts along with aggregate assets may be enough to complete markets, or mutual insurance assets may be needed.