arbitrage. Similarly, arbitrage affects the difference in interest rates paid on government bonds issued by the various countries, given the expected depreciation in the currencies relative to each other (see interest rate parity). Risks Arbitrage transactions in modern securities markets involve fairly low day-to-day risks, but can face extremely high risk in rare situations, particularly financial crises, and can lead to bankruptcy. Formally, arbitrage transactions have negative skew – prices can get a small amount closer (but often no closer than 0), while they can get very far apart. The day-to-day risks are generally small because the transactions involve small differences in price, so an execution failure will generally cause a small loss (unless the trade is very big or the price moves rapidly). The rare case risks are extremely high because these small price differences are converted to large profits via leverage (borrowed money), and in the rare event of a large price move, this may yield a large loss. The main day-to-day risk is that part of the transaction fails; this is called execution risk. The main, rare risks are counterparty risk, and liquidity risk: that a counterparty to a large transaction or many transactions fails to pay, or that one is required to post margin and does not have the money to do so. In the academic literature, the idea that seemingly very low-risk arbitrage trades might not be fully exploited because of these risk factors and other considerations is often referred to as limits to arbitrage. Execution risk Generally, it is impossible to close two or three transactions at the same instant; therefore, there is the possibility that when one part of the deal is closed, a quick shift in prices makes it impossible to close the other at a profitable price. However, this is not necessarily the case. Many exchanges and inter-dealer brokers allow multi legged trades (e.g. basis block trades on LIFFE). Competition in the marketplace can also create risks during arbitrage transactions. As an example, if one was trying to profit from a price discrepancy between IBM on the NYSE and IBM on the London Stock Exchange, they may purchase a large number of shares on the NYSE and find that they cannot simultaneously sell on the LSE. This leaves the arbitrageur in an unhedged risk position. In the 1980s, risk arbitrage was common. In this form of speculation, one trades a security