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Monetary policy glossary

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O

OIS
overnight index swap
open market operation
An operation executed on the initiative of the central bank in the financial market. With regard to their aims, regularity and procedures, Eurosystem open market operations can be divided into four categories: main refinancing operations; longer-term refinancing operations; fine-tuning operations; and structural operations. As for the instruments used, reverse transactions are the main open market instrument of the Eurosystem and can be employed in all four categories of operations. In addition, the issuance of debt certificates and outright transactions are available for structural operations, while outright transactions, foreign exchange swaps and the collection of fixed-term deposits are available for the conduct of fine-tuning operations.
opportunity cost
A measure of the costs of holding an asset, typically measured as the spread between its own return and the return on an alternative asset.
option
A financial instrument that gives the owner the right, but not the obligation, to buy or sell specific assets (e.g. a bond or a stock) at a predetermined price (the strike or exercise price) at or up to a certain future date (the exercise or maturity date). A call option gives the holder the right to purchase the underlying assets at an agreed exercise price, whereas a put option gives the holder the right to sell them at an agreed price.
output gap
The difference between the actual and potential levels of output of an economy, expressed as a percentage of potential output. Potential output is the level of output that can be achieved when the factors of production are utilised at non-inflationary levels.
outright transaction
A transaction whereby assets are bought or sold outright in the market (spot or forward).
overnight deposits
Deposits with next-day maturity. This instrument category comprises mainly those sight/demand deposits that are fully transferable (by cheque or similar instrument). It also includes non-transferable deposits that are convertible on demand or by close of business the following day. Overnight deposits are included in M1 (and hence in M2 and M3).