爱华网Some form of risk taking is inherent to any business activity. Somerisks are considered to be "natural" to specific businesses, suchas the risk of oil prices increasing or decreasing is natural tooil drilling and refining firms. Other forms of risk are notwanted, but cannot be avoided without hedging. Someone who has ashop, for example, can take care of natural risks such as the riskof competition, of poor or unpopular products, and so on. The riskof the shopkeeper's inventory being destroyed by fire is unwanted,however, and can be hedged via a fire insurance contract. Not allhedges are financial instruments: a producer that exports toanother country, for example, may hedge its currency risk whenselling by linking its expenses to the desired currency. Banks andother financial institutions use hedging to control theirasset-liability mismatches, such as the maturity matches betweenlong, fixed-rate loans and short-term (implicitly variable-rate)deposits.
在金融领域，对冲是指用于减少或回避另外一种投资风险的投资。对冲是被设计为降低意外的投资风险为最小的策略，同时也可从投资行为中获得利润。典型的说，对冲者可以买进一个他认为低于合理价格的证券或债券等投资，然后结合这些卖出相关或类似的证券或债券。这样，对冲者就不用理会整个市场的波动，而只关注被低估的投资部分的表现。HolbrookWorking（斯坦福大学的经济学家），对冲理论的先驱，称这种策略为从根本的投机，这个根本就是对冲理论价值与实际价值的差别。
在商业行为中本来就有风险。有些是天生的，如油田或炼油公司对油价涨跌的变化。有些是意料之外的，不使用对冲就不可以被避免的。如某人是个店主，他可以处理好竞争，低质量或不流行的货物，但是无法避免仓库的火灾，他可以买火灾保险作为对冲。不是所有的对冲都是金融产品，如生产者出口产品去别的国家可以卖出该国货币至所需的货币，这样即使将来该国货币贬值，生产者也避免了损失。银行和其他金融机构也使用对冲来控制资产负债的不匹配，如到期支票和应付款，固定比例的贷款和短期（不定期的）存款。
对冲交易
Example hedge
A stock trader believes that the stock price of FOO, Inc., willrise over the next month, due to this company's new and efficientmethod of producing widgets. He wants to buy FOO shares to profitfrom their expected price increase. But FOO is part of the highlyvolatile widget industry. If the trader simply bought the sharesbased on his belief that the FOO shares were underpriced, the tradewould be a speculation.
Since the trader is interested in the company, rather than theindustry, he wants to hedge out the industry risk by short sellingan equal value (number of shares × price) of the shares of FOO'sdirect competitor, BAR. If the trader were able to short sell anasset whose price had a mathematically defined relation with FOO'sstock price (for example a call option on FOO shares) the trademight be essentially riskless and be called an arbitrage. But sincesome risk remains in the trade, it is said to be "hedged."
The first day the trader's portfolio is:
Long 1000 shares of FOO at $1 each
Short 500 shares of BAR at $2 each
(Notice that the trader has sold short the same value ofshares.)
On the second day, a favorable news story about the widgetsindustry is published and the value of all widgets stock goes up.FOO, however, because it is a stronger company, goes up by 10%,while BAR goes up by just 5%:
Long 1000 shares of FOO at $1.10 each — $100 profit
Short 500 shares of BAR at $2.10 each — $50 loss
(In a short position, the investor loses money when the price goesup.)
The trader might regret the hedge on day two, since it reduced theprofits on the FOO position. But on the third day, an unfavorablenews story is published about the health effects of widgets, andall widgets stocks crash -- 50% is wiped off the value of thewidgets industry in the course of a few hours. Nevertheless, sinceFOO is the better company, it suffers less than BAR:
Value of long position (FOO):
Day 1 — $1000
Day 2 — $1100
Day 3 — $550 => $450 loss
Value of short position (BAR):
Day 1 — $1000
Day 2 — $1050
Day 3 — $525 => $475 profit
Without the hedge, the trader would have lost $450. But the hedge -the short sale of BAR - gives a profit of $475, for a net profit of$25 during a dramatic market collapse.
对冲交易
一个股票交易员相信foo的股票价格下个月将上升，因为这个公司使用了新式的更有效的方法生产。他想买foo股票来获取价格上涨的利润。但是foo的行业产品市场是反复无常的。如果交易员买入股票只是简单的根据foo股票价格被低估的理念，这个交易极有可能是失败的投机。
因为交易员对这个公司更感兴趣，他可以通过卖出等值的直接竞争者bar的股票来对冲掉行业风险。如果交易员能够卖空在与foo的股票等值的资产(如看涨期权对foo股票)的，交易可能会基本上是无风险的，被称为套利.但由于某些风险依然存在,在交易,他们说是"对冲"。
第一天这个交易员的账户:
多单1000股foo,单价$1
空单500股，单价$2
(注意空单和多单等值：股数*价格)
第二天,行业利好消息出台，foo作为行业较强公司，涨10%，bar涨5%
账户情况如下：
多单1000股foo,单价$1.1利润：$100
空单500股，单价$2.1 损失：-$50
交易员第二天可能会后悔，因为对冲减少了收益。但是第三天行业不利消息出台，全行业损失50%，因为foo较好，所以跌的也比bar少：
账户情况如下：
多单：
第一天：$1000
第二天：$1100
第三天：$550
损失：$450
空单:
第一天：$1000
第二天：$1050
第三天：$525
利润：$475
如果没有对冲，交易员可能损失$450，但是对冲赚了$475,最终在戏剧性的市场崩溃中净赚了$25我们常在外汇市场中见到的对冲交易有--非美高息之间的对冲，如这次美国次按风波，作欧元多的时候，补一手NZD放空就是防范集体的风险，和锁仓是不一样的。但是，具体的技巧需要更多的实践来检验。投机中的对冲虽然减少了利润，但是或许是获取稳健收益的一条金光大道。需要注意的是，利用不同的止损和止赢的策略是不同于简单的交叉盘保值做法。
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