country or the region: Price stability, i.e. inflation-targeting; the facilitation of maximum employment in the economy; the assurance of moderate, long term, interest rates. The central bank is the banker of the government and provides to the government a range of services at the operational level, such as managing the Treasury's single account, and also acting as its fiscal agent (e.g. by running auctions), its settlement agent, and its bond registrar. A central bank cannot become insolvent in its own currency. However, a central bank can become insolvent in liabilities on foreign currency. Central banks operate in practically every nation in the world, with few exceptions. There are some groups of countries, for which, through agreement, a single entity acts as their central bank, such as the organization of states of Central Africa, which all have a common central bank, the Bank of Central African States; or monetary unions, such as the Eurozone, whereby nations retain their respective central bank yet submit to the policies of the central entity, the European Central Bank. Central banking institutions are generally independent of the government executive. The central bank's activities directly affect interest rates, through controlling the base rate, and indirectly affect stock prices, the economy's wealth, and the national currency's exchange rate. Monetarists and some Austrians argue that the central bank should control the money supply, through its monetary operations. Critics of the mainstream view maintain that central-bank operations can affect but not control the money supply. Open-market operations Open-market operations (OMOs) concern the purchase and sale of securities in the open market by a central bank. OMOs essentially swap one type of financial assets for another; when the central bank buys bonds held by the banks or the private sector, bank reserves increase while bonds held by the banks or the public decrease. Temporary operations are typically used to address reserve needs that are deemed to be transitory in nature, while permanent operations accommodate the longer-term factors driving the expansion of the central bank's balance sheet; such a primary factor is typically the trend of the money-supply growth in the economy. Among the temporary, open-market operations are repurchase agreements (repos) or reverse repos, while permanent ones involve outright purchases or sales of securities. Each open-market operation by the central bank affects its balance sheet. Monetary policy Monetary policy is the process by which the monetary authority of a country, typically the