Three Basic Issues that Arise when Using Informational Restrictions in SVARs*
讨论了在SVAR中使用符号或其他信息限制时，必须处理的三个问题：限制条件需足以区分冲击、调整识别集以对应相同大小的冲击、以及未完全区分冲击时的估计方法，并提出了三角SVAR作为解决方案。
Abstract When sign or other informational restrictions are used in SVARs, impulse responses are only set identified. Three issues need to be addressed when finding such sets. One is that the restrictions must be sufficient to separate the shocks. Failure to do so can result in unacceptable structural equations, for example two supply curves in the SVAR. Another is the need to adjust the identified set so that the responses are to the same size shock. Otherwise the range of responses that are being found may simply reflect different shock sizes. The third issue is estimation of the SVAR when all the shocks are not separated. Researchers are often unwilling to set out sign restrictions to separate all shocks and so we describe what can be done to accommodate that attitude by using a triangular SVAR that parallels what is used with exact restrictions.