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arXiv 1106.3496q-fin.PRq-fin.RM
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首次违约时间对双边CVA的影响

Impact of the first to default time on Bilateral CVA

Damiano Brigo, Cristin Buescu, Massimo Morini

摘要:

我们比较了两种不同的双边交易对手估值调整(BVA)公式。第一个公式是一个近似值,是基于减去两个单边信用估值调整(CVA)的公式,从交易中的两个不同的当事人。该公式只是双边风险的简化表示,并忽略了第一次违约时就会启动平仓程序。因此,它涉及双重计算。我们比较这个公式与完全指定的双边风险公式,其中第一个违约时间被考虑在内。后一个正确的公式取决于双方之间的默认依赖,而简化的一个不。我们还分析了一个候选人的简化公式的情况下,更换平仓违约后,ISDA的建议,我们发现简化的公式是相同的无风险平仓的情况下。我们分析了在两个简单产品中使用简化公式时遇到的错误:零息债券,其中暴露是单向的,以及股票远期合约,其中暴露可以是双向的。对于后一种情况,我们采用了一个双变量的指数分布,由于Gumbel模型的联合违约风险的交易双方。我们提出了一些现实的情况下,简化的公式有很大的不同,从正确的。

英文摘要:

We compare two different bilateral counterparty valuation adjustment (BVA) formulas. The first formula is an approximation and is based on subtracting the two unilateral Credit Valuation Adjustment (CVA)'s formulas as seen from the two different parties in the transaction. This formula is only a simplified representation of bilateral risk and ignores that upon the first default closeout proceedings are ignited. As such, it involves double counting. We compare this formula with the fully specified bilateral risk formula, where the first to default time is taken into account. The latter correct formula depends on default dependence between the two parties, whereas the simplified one does not. We also analyze a candidate simplified formula in case the replacement closeout is used upon default, following ISDA's recommendations, and we find the simplified formula to be the same as in the risk free closeout case. We analyze the error that is encountered when using the simplified formula in a couple of simple products: a zero coupon bond, where the exposure is unidirectional, and an equity forward contract where exposure can go both ways. For the latter case we adopt a bivariate exponential distribution due to Gumbel to model the joint default risk of the two parties in the deal. We present a number of realistic cases where the simplified formula differs considerably from the correct one.

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