Keynes believed the demand for money depended on income and interest rates. Money was held to facilitate normal transactions and as a precaution for unexpected transactions. For both of these motives, money demand depended on income. People also held money as an asset, for speculative purposes. The speculative motive depends on income and interest rates. People hold more money for speculative purposes when they expect bond prices to fall, generating a negative return on bonds. Since money demand varies with interest rates, velocity changes when interest rates change. Also, since money demand depends upon expectations about future interest rates, unstable expectations can make money demand, and thus velocity, unstable.