The ‘excess sensitivity’ as the method of estimating the underground economy by using currency modeling is found to be unreliable. In general, there are two major weaknesses in the method. First, the key assumption, in assuming the equality of velocity of money between the official economy and the underground economy, is very unrealistic. Second, the method is found to be non robust due to the unit measurement and scale change. More specifically, the application of the excess sensitivity method using the single-step error correction model (ECM) in Bajada’s paper is very weak because there is no cointegration analysis as the prerequisite of ECM modeling. In conclusion, the possibility of using a currency demand approach in estimating the size of the underground economy is still unclear like ‘black box’, and in particular, the excess sensitivity method should be thoroughly revised.

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