In some periods such as the credit crisis, liquidity in financial markets declines dramatically, and many surplus units no longer participate in financial markets. Yet, if the markets are efficient, prices should adjust to existing economic conditions, and one might argue that investors should always be willing to participate. Write a short essay that explains the logic behind why participants may temporarily disappear, causing illiquidity. Do you think the credit crisis in the 2008-2009 period caused illiquidity in the financial markets, or did illiquidity in the financial markets cause the credit crisis?