Europe has a well-developed financial sector. Many European cities are financial centers, the largest of which is the City of London. The financial sector in continental Europe was supported by the introduction of the euro as the single currency. This made it easier for European households and firms to invest in companies and place money in banks in other European countries. In addition, the euro has established itself as a global "reserve" currency, meaning that many non-euro countries hold reserves of the currency as part of their foreign exchange reserves, which are primarily used in merchandise transactions. The euro is currently the second most widely used reserve currency in the world after the US dollar, with some countries such as Russia using the euro as their main foreign reserve currency.
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