Suppose that Japanese investors suddenly decide that U.S. investments look unpromising, and unilaterally attempt to cash out $500 billion worth of their U.S. investments (stocks, bonds, etc). Keeping the balance of payments identity in mind, can they in fact withdraw their money from the U.S.? (And if so, how?) What is the impact on the exchange rate and on the U.S. balance of payments (i.e., on the current and capital accounts)?